1970 Checkmate MX-14 + 1250 Super BP Stacker + 1973 1500 High School Resto

[starviper10]

I'd like to preface this by thanking all of you for sharing your awesome projects on this site, as I would likely not have started (or purchased) this project without d̶r̶o̶o̶l̶i̶n̶g̶ ̶o̶v̶e̶r seeing your amazing transformations. Many of those restoration threads read like books, and they have certainly offered great inspiration for me. My only criticism is that you all make perfect work look too easy at times, and therefore instill false confidence in us ignorant rookies lol (multiple examples to follow :D). I didn't think of my work as worthy of a resto thread on here, but some of my friends on this forum have been trying to convince me otherwise. If for nothing else, perhaps at least people could learn what NOT to do.

The term "biting off more than you can chew" very accurately describes this endeavor. What started as a simple engine rigging project with a plain jane 100hp "Tower of Power" long shaft Merc became a complete restoration (in progress of course) and piecemeal of a 1969 1250 Super BP Stacker replica. So this is my unintentional, yet first, and seemingly everlasting attempt at a boat restoration.

The Hull Acquisition Story
Over the summer of 2013, I really wanted my own small boat project, but I couldn't find anything I liked that I could also afford. Having prior experience on only inboards and small (35hp or less) outboards, I was a little apprehensive of larger outboards, as I really liked the simplicity of inboards. I was really set on the 1987/88 Checkmate Playmate 13' models, but they were all rather costly and difficult to find (53 made I think?). As summer ended, I started my junior year of high school and Labor Day Weekend rolled around, and we were headed a few hours east to a Labor Day bash. I'm very blessed to have a very supportive father, as he said "Why don't we bring the little trailer and go 'boat picking' on the way there?" Sure enough, we set out in our 86' Bronco and empty 15' jet ski trailer on the hunt for a small, but cool boat for sale. We drove around almost every lake on the way there, surely looking completely lost to the locals, all the while disturbing the peace with the cherry bombers on the truck. Someone went so far as to ask if we had lost a boat off of our trailer somewhere. We followed up on any interesting craigslist finds I found, concluding with this hull.

The seller was asking $425 for the hull & trailer package, and the only info he had on it was that it was 14' long, purchased out of an auction, and some guy redid it a while back. There was no paperwork of any kind, no engine, rigging, interior, seat bases/mounts, controls, or steering helm. There were 4 gauges with shades, 3 of which were period correct (including a water pressure gauge which I'd later find out was pretty rare and worth over $100). There was nice carpeting inside, so I was unable to see the floor, but it felt solid. As for the transom, I knew to be cautious as I had heard of many deceivingly strong, yet completely rotten transoms. It felt solid to me, and unfortunately there was a thin aluminum sheet over it (which I'd learn later to be hiding something) so I couldn't see much. The paint had a slight metal flake to it on the deck, but it was chipping in areas. The stripes are actually vinyl tape, not paint, yet easily fool anyone from 30+ feet away. There was a hook looking feature at the start of the chines at the bow that made me think Checkmate (I'd later find out my hunch was correct).

When the seller walked away momentarily, I turned to my dad and said "I think it's a Checkmate, but I'm not sure." We agreed that it would be worth a $100 gamble if he'd take it. My dad, being the salesman that he is, said to the guy "You have no idea what boat this is, and we have no idea what it is, so how about my son gambles in buying the hull for $100, and you can paint and flip the trailer for a few hundred bucks to someone else?" He accepted, then we moved it onto our trailer, and then we arrived to the Labor Day bash with an old, unknown boat in tow.

To keep this first post from becoming a novel, I'll quickly summarize what (little) progress has occurred over the last 7 years. I thought I'd be much further along, if not complete by now, but other priorities have been in place, namely high school, college, internships, and co-ops. Over the next few days I'm hoping to have this thread updated to where I'm at currently. There are some relatively big decisions I need to make soon, and I would greatly appreciate any input you all might have, as this is all entirely new territory for me.

Summary
- hull condition worse than expected: rotten transom, poorly replaced stringer & floor, lots of filler covering large areas
- hull restoration: new stringer, floor, transom, transom knees, seat box/mount, and seats
- motor selection progression

1968/69 100hp long shaft
Frankenmerc (1350 powerhead, Super BP mid, Twister/T2 adapter, 1500XS lower, louvered cowl)
1969 1250 Super BP replica (normal 1350 powerhead) + 1973 1500 Circle C short shaft (for when I don't want the inevitable noise complaints & fines)

- misc parts acquired

dual opposed ride guide steering system complete with wood grain steering wheel (I know, more correct for Hydrostream, not Checkmate, but I like the wood grain better than black rubber)
Checkmate optional trim tabs
correct gauges (speedo, tach, water pressure, battery, trim)
another boat: Checkmate MX-15 (great deal and came with the 1500 shorty along with a bunch of other parts I used on this MX-14)

- assembly: the bare minimum was assembled enough to run it on the water in August 2017 to get a feel for it
- currently in a disassembled state, with the plan to not reassemble until everything is painted

As you read through this, please feel free to let me know if there's anything I'm doing wrong. This project is incomplete, so there is still the opportunity to fix things properly. Contrary to most of my generation, I do not know everything, and I willingly admit that. That being said, there are times when I'm stupidly ignorant and stubborn (glassing the external edge of the seat base without cutting a radius into it for example). Please call me out in those situations. As a fiberglass rookie, I know there is plenty of room for improvement. I hope that this is not the only fiberglass project I will have, so I hope to better my abilities for the next project.

Also, I'm still figuring out paint ideas for this, so if you have any suggestions/ideas, please share them.

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[tnelsmn]

Thats a sweet little boat! You're in the right place for help. These I6's are really growing on me and I could see myself doing another restoration with an I6. Looking forward to reading more.

[starviper10]

I figure I’ll start from the beginning with the craigslist ad and pictures of the boat when I purchased it. There was just one picture in the ad, showing a 4 cyl merc on it. The seller said it had either a 80 or 85hp Merc on it before. Unfortunately there was no Checkmate ID plate (typically located near the controls). There were many holes in the deck and transom from likely many different controls and engines. The gauges were a cool bonus, as 3 are of the correct vintage (speedo, water pressure, and battery). I actually sold the tach that was not of the incorrect vintage for $20, so that meant I was really only $80 deep into the boat. When I removed the gauges I noticed that the gauge holes in the dash were not sealed, and there was a small bit of rot, but nothing terrible. The transom and the floor both felt solid, but again this was my first experience with this style boat, so I wasn’t confident. There was an odd sheet metal piece with a momentary button covering up a relatively large hole. I later figured out that there was likely a stock 3 button power trim control panel mounted there (located such that one's throttle hand could work the trim without letting go of the throttle).

Posted: 2013-07-26, 1:45PM EDT
Speed boat w/Trailer NO TITLE No Motor - $425 (elkhart)
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have a project speed boat Minus the motor.needs seats,but overall great boat, open to all serious trades.looking for xbox360. Txt or call.once again has NO TITLE FOR BOAT OR TRAILER, can write a bill of sale.


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[largecar91]

I owned a 1970 MX 14 back in the 70's. It was a factory race hull. It was a blast. Very fast little boats but a handful to drive with the rounded keel.

[1954bmw]

Thought you had this finished in 2017, all it needed was seats, I followed it on the Checkmate web site??

[starviper10]

I owned a 1970 MX 14 back in the 70's. It was a factory race hull. It was a blast. Very fast little boats but a handful to drive with the rounded keel.

Yeah unfortunately the pad is narrow with rounded edges, and the strakes are rounded as well. It's definitely not built like a Hydrostream or Allison. One of the questions I had was with regard to hull modifications. I'm not sure what's worthwhile, or more importantly what's feasible, with regard to attempting to widen the pad, or at the very least square the edges. I've seen some threads online about it, but I haven't researched it enough yet. I've never done bottom work like this before, so I'm also not sure what's feasible for a newbie. If you guys have any thoughts on this that would be much appreciated.


Thought you had this finished in 2017, all it needed was seats, I followed it on the Checkmate web site??

So that was just a quick assembly and splash. I had never driven this hull before, or anything similar really. I wanted to get a feel for it before I'd go ahead and pour a lot more time and money into it. I also figured that after running it, I'd have a better idea of where I'd like the fuel tank, battery box, seats, the throttle, gauges, switches, etc. It also acted as a mid build motivator, as it was really fun to drive and I was hooked. I kept it assembled and running up until this past fall, and now it's mostly torn apart again. Now is the time to complete the restoration.

[1954bmw]

Did you finally get rid of that MX15??

[largecar91]

Set up right it'll run 80. Mine was the funnest boat I ever owned.

[starviper10]

Did you finally get rid of that MX15??
Nope

Set up right it'll run 80. Mine was the funnest boat I ever owned.

Do you mind sharing more details of the setup you had (engine, install height, any setback, checkmate trim tabs, center steer etc)? Any pictures?

[starviper10]

I forgot to mention that I went on the Checkmate forum the day after buying this boat and the very knowledgeable members there were able to confirm that it is a Checkmate, so that was great news. The parts and engine search began next. I found a NOS correct vintage tach at a local marina.

Initially, my plan was to put a long shaft 100 hp on it, as I wasn’t going for top speed, and the boat was rated for 100 hp. Oh how that plan would change :D. My first outboard purchase larger than 35 hp came in the form of a pair of 1968 & 1969 Mercury Inline 6 “Tower of Power” 100 hp long shaft engines, a little less than a month after buying the hull. I was able to see the 1969 fire up and run. It was in need of a water pump (little water at low rpm), and an o-ring on the drain plug on the lower unit (chocolate milk for gear lube). Compression wasn’t great but at least fairly consistent from cylinder to cylinder (120/120/119/121/117/118 cold). The 1968 engine was stuck in gear, had no signs of leaks in the gearcase, and had slightly more consistent compression (120/119/120/121/121/121 cold). Included in the deal was two sets of controls, one of which was in very good shape, the other not so much. My thought was to buy two decent engines to make one good one.

The seller of these two engines had the 1969 engine mounted on the back of this flat deck trailer like it was a transom of a boat, with the 68 laid over on the front of the trailer. He simply backed it in and started the 1969 up. After buying it, he used the crane to put it on my Checkmate. I had never seen a bucket boom used for lifting outboards lol. The trailer I had the Checkmate on before was meant for a waverunner, so it didn't have a high enough capacity to handle the hull with an engine. We borrowed my dad's ski boat trailer for the meantime. It sure looked weird but it worked. It was great to see a motor on it.

I later built a dual engine stand in the garage for them.

Not sure why some pictures are rotating on me...:confused:

[largecar91]

Mine was a center steer race boat. Probably around 300 lbs. No set back. Had factory trim tabs. For top end I ran it as high as possible and still suck water. I had a 72 Merc 140 short shaft.

[1954bmw]

Is the white of the hull original gelcoat or is it paint??? I painted my first MX15 and always wished I had not, had concerns about sitting in the water at Cumberland for a week at a time, scratches from rolling up under docks. If it is the original gelcoat, do you think you could save it, my MX14 only needs a good polish??? What are your thoughts on seats, I have some plastic buckets for skinny a$$es, they are about 19 inches by 19 inches, give me a phone number and I can text some pics.

[starviper10]

Mine was a center steer race boat. Probably around 300 lbs. No set back. Had factory trim tabs. For top end I ran it as high as possible and still suck water. I had a 72 Merc 140 short shaft.

That sounds like an awesome setup. Do you happen to recall what that max height was? And was that a stock lower unit? I intended to build up the 19" to be 3.5" higher, but it ended up being a little bit more than 3.5" due to the rounded corners of the transom clamp brackets that I totally spaced on taking into account. The prop shaft is ~0.85" below the pad. I've not had any water pressure issues, but I have only ran a 6 hole 1500xs gear case.


Is the white of the hull original gelcoat or is it paint??? I painted my first MX15 and always wished I had not, had concerns about sitting in the water at Cumberland for a week at a time, scratches from rolling up under docks. If it is the original gelcoat, do you think you could save it, my MX14 only needs a good polish??? What are your thoughts on seats, I have some plastic buckets for skinny a$$es, they are about 19 inches by 19 inches, give me a phone number and I can text some pics.

The deck is definitely painted, and painted rather poorly, as it is peeling in many areas. In the few areas that I have sanded on the deck there is blue metal flake. As for the hull, I haven't seen any signs of blue yet, but I also haven't started sanding it yet. It has too many scratches to have any hope of saving it. As for seats, I have mostly finished rebuilding a rotten set I got for free that I believe to be the correct style. Give me a few days here to get this thread up to date with where I'm at now and you can see what I did. I think they will turn out well.

[starviper10]

The next discovery with this hull was a bit of a bummer for me. After removing the thin aluminum plate on the transom (a very asymmetric plate I might add), I found some split lines. It appeared that someone at one point thought a 19” transom was too tall, so they made a cut out to drop the motor lower. I don’t understand how 19” could be too tall for any engine that would go on this (excluding 12” race engines of course), as a short shaft inline 6 Merc can drop right on and run perfectly fine. Even if you felt it was too tall, I feel like adding one of those midsection extension spacers would be far easier than chopping the transom. Regardless, someone later put the cut out piece back in and tried to cover it up.

Between this poorly sealed cut out, the poorly sealed splash well drains, and the poorly sealed extra outboard mounting holes, it was clear that this transom was rotten, and needed replacement. It was then that I realized just how deceivingly strong a rotten transom can be, as the transom didn’t flex at all when that 300lb 100hp engine went on it. This was also when I discovered that the boat was likely originally blue metal flake, or at least part of the transom.

We had to switch trailers again, but this time we used the convenient concept of buoyancy instead of our backs. It was cool to see it in the water. At least it floated :thumbsup:

I pulled the carpet out soon after to check out the floor. It felt solid, but again so did the transom at first. The floor was not completely glassed over, as it just had some tabbing strips to the hull, leaving the center completely exposed. You could see some of the plywood delaminating.

I forgot to mention that this boat purchase included a #13 pool ball. When buying the boat, I jokingly asked the seller if that was included and he said it of course it goes with the boat. My dad was born on Friday the 13th, so in contrast to most of the world, 13 is his lucky number. He told me it would be bad luck to remove the pool ball, so for no other reason than being superstitious and afraid of bad luck, I’ve kept it in the bilge there :D.

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[starviper10]

I didn’t get much progress on this project for the rest of the fall, the winter, and the spring. My junior year of high school did not lend itself well to have free time to work on it, with AP and honors courses, along with high school sports and ACT/SAT exams for college applications.

However, once summer rolled around I was eager to get back to work on the boat. I sourced a set of the optional Checkmate trim tabs. Unfortunately, mine had some typical cracks. When mounted correctly, they are parallel to the water, in contrast to the common trim tab that installs parallel to the deadrise. Instead of altering the angle in which the hull rides in the water like a deadrise parallel trim tab, the motivation behind this style application is to reduce chine walk potential by essentially acting as a tripod with the pad. As largercar91 mentioned, these hulls can get pretty unstable at high speed due to their relatively narrow and rounded pad. I hung the trim tabs from a broom stick handle to get a visual mock up.

As for engine progress, I pulled the lower units off. I had a local, inline 6 Merc experienced marina pull apart the lower unit that was stuck in gear. It was simply a shift shaft issue, so that was good to hear.

However, it was at this stage that I started deviating from the long shaft route, as I noticed some short shaft mid sections laying around at that marina. I had been scrolling through forums for a little while, looking at short shaft inline 6 Mercs, and I really preferred the short shaft look over the long shaft. Seeing them in person at the marina pushed me over the edge in the decision, as I was hooked. So my next step was removing the powerheads.

I also started work towards the transom removal. The little transom cut out fill in piece came out rather easily. The transom condition didn’t look any better underneath it. I built some better bunks for supporting the hull in preparation for when the hull would lose a lot of structural strength when the deck and old transom are torn out. The rub rail rivet drilling process began as well.

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[starviper10]

The Checkmate forum has a great gallery full of old Checkmates, many with Merc inline 6’s. Here are just a few of the ones that I really like. Between these pictures, and all the short shaft and racing Mercs on this forum, I was really hooked on the look. I included some pictures of the original brochure from 1971 as well.

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[starviper10]

The deck came off next, after a lot of rivet drilling and glue breaking. It was a completely new experience for me, splitting a boat in half.

There appeared to be some seacast perhaps, between the splashwell and the transom. I was surprised to see that the bow deck stringers were wider than they were tall, as structurally that doesn’t seem logical at all. The fiberglass wasn't tabbed well either, as there seemed to be large air gaps underneath. In a restoration thread on a 15ft Checkmate, I noticed that it had tall stingers, likely made of ¾” plywood. When I walked across the deck on my hands and knees, I could feel the deck bend more than I was comfortable with. My plan is to mimic the design of the 15ft Checkmate.

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[largecar91]

Here's a few pics that I have on my computer at work. I have some regular Photos at home but they are not scanned on the computer.

[starviper10]

Here's a few pics that I have on my computer at work. I have some regular Photos at home but they are not scanned on the computer.

Thanks for sharing those. I love that rooster tail picture! If you come across any others please feel free to post them.

[starviper10]

Transom removal occurred next. I was really shocked at how deceivingly strong that transom appeared, as clearly it was totally rotten. Although at $100, I really couldn’t complain. As I mentioned earlier, I likely could have sold the gauges and shades for a small profit, or at the very least broken even. If for nothing else, this offered a great lesson in boat purchasing for me, as I’ll know what to look for on the next one.

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[starviper10]

The next engine part purchases consisted of a freshly rebuilt 1500XS 6 hole lower unit and a 950 short shaft mid section. The 1500XS came from MN, and the mid section from VA, both from members on here. I was quick to do a mock up on the boat with an empty cowl, even though there was no deck or transom. I was absolutely thrilled with the short shaft look.

The 1500XS lower unit was not really planned. I was on the hunt to upgrade to a newer inline 6 lower unit. They have stainless steel shafts, so no worry of the pitting around the water pump seal like the older steal shafts. They are also slightly longer, allowing the leading edge to be less blunt. Some of the later model ones also have a swept back skeg.

I saw this 1500XS lower unit pop up for sale, and I was able to buy it for much less than our local, inline 6 experienced could rebuild one for. This one came from a very experienced prior Mercury employee, and he had already pulled it apart to inspect and reseal. This has that stainless steel shaft and that longer housing design. The 1500XS lower units never had the swept skeg, but I honestly prefer the straight skeg because it’s more period correct.

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[starviper10]

Next up was the bulkhead removal. I’m not sure if this was stock, as there wasn’t any foam inside the bulkhead. I found an old plastic rope bag instead. I also cut out the remainder of the transom, at the very bottom.

I did come across some creative uses of sheet metal. At the stern, there were some sheet metal pieces spanning gaps between the floor and the transom, underneath fiberglass. On the opposite end of the floor, there was also some sheet metal hidden underneath fiberglass. It was at that point that I realized that the floor was likely replaced at some point, and replaced poorly.

Also pictured are some spider cracks on the deck that I didn’t really take notice of yet. I believe I found the cause though, as the dashboard piece had a crack in the tabbing to the deck directly underneath the spider cracks. I’m hopeful that after repairing that tabbing, the spider cracks won’t reappear.

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[starviper10]

I started on the paint stripping of the mid section next. I also discovered that someone cut big square holes in the splashwell. I’m guessing that the same genius that made the cut out in the top of the transom realized after the fact that the thumb screws on the clamp brackets would require holes in the splashwell such that they could drop through at the lower engine install height. There were old rigging holes that were filled in as well. All the holes were poorly repaired, as it didn’t take much to pound them out. There was a lot of filler in general in the splashwell to make it smooth.

The next part purchase was a small ear 24p chopper. The plan was to jack the engine 3.5” off the 19” transom and run small ear chopper props. Naturally, I wanted to get an idea what it would like, so I made another mock up.

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[starviper10]

I was on the hunt for a complete power trim system when I came across this late model long shaft mid section, lower unit, and power trim system package for sale. The seller wouldn’t separate just the trim system, and the asking price was a great deal, even if it was just for the trim system, so I bought the whole package. Two of the hydraulic lines looked almost brand new, and the other two were actually SS braided.

My goal for the steering system was a dual, opposed ride guide rack & pinion system, if I could find the parts, as some components have become hard to find. One part that is particularly rare is the secondary steering cable tube that bolts to the tilt tube. The MN guy that sold the 1500xs lower unit to me had one for sale that I bought.

I came across a great deal on a short mid with a power trim system on craigslist and bought it. I wanted to have a backup trim system, as I heard that certain replacement parts are not available for them. That was when I first learned of the two different diameter trim cylinders that were made.

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[starviper10]

I finally completed the structural demolition of this hull with the removal of the floor and stringer. While the floor wasn’t totally rotten, it was delaminating, and lacked fiberglass in the middle. The tabbing to the hull was not adhered well at all, as it was surprisingly easy to remove (tabbing came out in large sections). I had the angle grinder with the cutting disc all ready to go, but I ended up only needing a crowbar to remove everything. There was a lot of 5200 used to fill in the gaps between the floor edges and the hull.

When I pulled the floor out, I was shocked to see that I had also pulled the stinger up with it, as it was still attached to the floor. Just when I thought all the hidden poor work had been discovered, I come to find that the floor and the stringer were constructed of 2 pieces, screwed together with sheet metal strips. Even worse, there were gaps between the bottom of the stringer and the hull, evident by the fiberglass/resin that leaked under the stringer. I still don’t understand why anyone wouldn’t replace the floor and stringer with one piece of lumber. It’s such a short stringer, so it’s not like you can use length as an excuse (less than 8 ft long).

I suppose I should give some credit, as at least the two piece floor overlapped the two piece stringer…

I was also slowly working on creating a CAD model of the boat. I wanted to play around with different rebuild ideas for the stringer, floor, transom, and transom crossmember/knees.

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[starviper10]

Here is the first Super BP component I got my hands on. I was not actively looking for any BP parts, but I came across an eBay ad for a lower unit out of CA, and I noticed that the mid section was not a typical stock mid. I confirmed with some inline 6 experts that it was in fact a studs up 15” 1000/1250 Super BP mid (https://www.screamandfly.com/showthread.php?322264-Mercury-1000-BP). The first two pictures are from the ad, with the powerhead and lower unit mounted. The mid didn’t have a serial number plate, so even if the powerhead was a 1000BP powerhead, it wouldn’t be worth any more than a typical 100hp powerhead. For it to be a 1000 Super BP, it would have 115/135 transfer port covers and a cast in starter bracket. Note that this mid has the adapter to be able to run any SSM or stock lower unit, in contrast to the unique bolt pattern of the BP lower units. These adapters (and BP mids in general) are actually rather hard to find.

The seller didn’t seem to know much about this, and wasn’t against parting it out. So I put an offer out on just the mid and he took it. I really liked the look of the BP mid (yet another mock up shown below), so my plan at the time was just to run the 100hp powerhead on it with the 1500XS lower unit. Little did I know I’d find other BP parts later down the road…

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[1954bmw]

[QUOTE=starviper10;3197127]Nope


Do you have a title to the MX15???

[starviper10]

Hopefully I haven’t bored anyone yet with the relatively little amount of progress that occurred over the first 3 years of this project. Other than cutting out the old rotten structure, I really only bought parts. However, I had an excellent opportunity over my 2016 winter break as a sophomore in college to make a lot of progress on the structural rebuild of the hull. During that 4 week winter break, I returned to a local marina that I had worked at the summer before. My boss knew about my project, and offered to let me bring the boat in and to help me with the fiberglass work, but only if I could help him finish up some customer boat projects first. So for the first 2 weeks I worked there on customer boats, and then I brought the Checkmate in for the last 2 weeks. That 2 week period was the most amount of time (~90 hours), and the most amount of progress I had achieved in such a short timeframe on this boat. I was able to complete the transom, stringer, floor, and transom knees.

This was a real turning point for this project. I had such little fiberglass experience before this, so I really needed some guidance and help. My boss went above and beyond, offering up a bay and his guidance & assistance. The best part was that I did pretty much all the work myself, with the exception of the occasional example work he’d perform for me to follow. However, glassing in the transom was definitely a two person job, and a job I did not want to mess up.

Looking back, there are definitely some things I would have done differently. Given that this project started in high school and continued through college, I didn’t have the biggest budget, so there was likely some better, more expensive material selection options I could have gone with. My boss was not familiar with coosa, so we went with marine grade plywood. Having seen how many of you are experienced with coosa and willing to share your methods, I think I’d definitely like to use coosa on the next boat project, if budget allows of course.

All in all, I think this boat has provided a great first experience for me with fiberglass work. I know it’s not perfect, but I also know that it’s likely wrong to expect perfection on my first attempt. That would be rather arrogant of me and disrespectful to fiberglass professionals to think that I could learn how to master fiberglass work in such a short time with such little experience. Given that this is a small boat, and I paid all of $100 for it, I think it makes a great first time project, as it’s not a rare or large or expensive boat if I totally screw it up.

That being said, please feel free to point out anything I overlooked or did incorrectly. I’m splitting the deck and hull again to replace the deck structure, so there’s opportunity to go back and make some modifications if need be, but within reason of course.

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[starviper10]

Structure wise, I rebuilt the stringer, floor, transom, and transom crossmember identical to how it came from the factory. However, I added transom knees inspired by the MX-15. The MX-14’s were rated for 100hp, while the MX-15 (15ft) went up to 150hp. Other than being wider, the only structural transom difference between the MX-15 & the MX-14 is the presence of transom knees on the MX-15. With my plan to raise the engine off the transom, I wanted to make sure the transom was well built.

The first install was the transom, comprised of 2 sheets of ¾” marine plywood with CSM between & on both faces, and resin around the edges to seal (all wood was completely sealed before bonding to hull). Screws sandwich the middle CSM layer. The crossmember is constructed the same way to essentially create a 2x4. The crossmember is screwed to the transom on edge with a layer of CSM between, followed with CSM tabbing above and below. I used some resin jelly to fill the gap between the transom & the hull before the final install. The transom went in for the final time with 2 layers of CSM between it and the transom skin. Clamps & screws through some lumber compressed the transom while curing. I later tabbed it to the hull.

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[starviper10]

The stringer construction is identical to the transom & crossmember (screws sandwiching a CSM layer between two ¾” marine plywood sections with CSM on both outer faces). It was installed with 2 wet layers of CSM between it and the hull. I overlapped 2 tabbing layers of CSM on each side to the hull.

Two wet CSM layers went between the stringer and the floor, with screws as well. I found that having a marina full of stored customer batteries was rather convenient to weigh both the stringer and the floor down.

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[starviper10]

The transom knees went in last, and they were built just like the stringer, transom, and crossmember (screws sandwiching a CSM layer between two ¾” marine plywood sections with CSM on both outer faces). Wet layers of CSM went between the knees and the floor, transom, and crossmember. CSM tabbing was later added as well.

This concludes the winter break 2016/17 work. It was very motivating for me to get to this point. Leading up to this point, I was pretty bummed about all the rot, and I wasn’t really sure if the fiberglass work was something I could learn to do myself. I was very lucky to have this great opportunity to make a lot of progress. This was all thanks to a great boss who enabled this by not only letting me bring my boat in, but by helping and guiding me as well. I wasn't even set up garage/shop and tool wise to complete this work.

Looking back, I likely should have used 1708 in certain areas. Obviously I can’t go back and change that now, but I could go over the top of the floor and add some tabbing to the transom & knees with 1708.

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[starviper10]

I came across a guy in MN looking to downgrade from a 1350 to something smaller, as he said it was too much for his boat. The motor was a long shaft with a jet pump, and 145 psi even across all 6. I still had my two 100hp long shaft motors, albeit both torn down to powerheads, mids, and lower units. I wasn’t actively looking for more power, but after realizing there’s little weight difference between the 100 & 135, and recalling that I overbuilt the transom, I was very tempted.

So I asked if he'd take a 100 hp powerhead + 20” mid combo in trade for his 1350 + 20” mid (I had no need/desire for a jet pump). He simply asked for a set of controls for the value difference. I figured I'd better jump on it, as there can't be too many people willing to trade a 135 for a 100. It needed wiring and fuel hoses, but as do most all unrestored inline 6’s. The high and even compression numbers were what really got my attention.

I put one of the 100’s together, and made sure it still ran. My dad and I then took a day road trip up to MN and back during my spring break to swap motors. The 1350’s will drop right onto a Super BP mid, so I was headed down the route of having a “Frankenmerc” motor comprised of a 1970 1350 powerhead, 1969 1000/1250 15” Super BP mid, and 1500XS lower unit (1976-78).

First two pics are of the 100hp & controls I traded for the 1350 (last 2 pics).

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[99fxst99]

Great thread. Keep the updates coming!

[tnelsmn]

Looking back, I likely should have used 1708 in certain areas. Obviously I can’t go back and change that now, but I could go over the top of the floor and add some tabbing to the transom & knees with 1708.


I was just going to add that some 1708 would probably be a good idea with some of the tabbing in work. :thumbsup:

Excellent thread! Cool to see it come together so fast since the project is already finished, unlike the 1.5 year long thread of mine haha.

[starviper10]

I was just going to add that some 1708 would probably be a good idea with some of the tabbing in work. :thumbsup:

Excellent thread! Cool to see it come together so fast since the project is already finished, unlike the 1.5 year long thread of mine haha.

Haha I wish it was done! Still a ways to go. Still need to replace deck structure, and prep it all for paint. I just went through your restoration thread for the first time, and I have to say I'm blown away. It sounds like this is your first restoration as well, kind of hard to believe with how professional your work is!

Also, thanks for the feedback on the fiberglass, I'll definitely add that tabbing. Please feel free to let me know if you see any other improvements that are needed.

[1954bmw]

Come on, Ohio is still locked down, looking for some more progress!!!!

[starviper10]

The next step of this project is likely rather unexpected, as it came in the form of the purchase of a second Checkmate. To most people, the purchase of a second boat, in much worse condition, likely seems completely illogical as an aid in the restoration of an existing project boat. Yet it seems perfectly justified to myself, and luckily my dad, and I would guess most of you here on this site. My mom on the other hand, wasn’t totally convinced, but I’m very thankful that she still let me park this crappy looking boat in the driveway for a couple weeks to strip it down to a bare hull.

This is the 15ft version of mine, called an MX-15. What really grabbed my attention was the 1500 short shaft on the back. The late model short mids are very hard to find. Note that this had a 5” extension on it. There’s also a louvered cowling on it, which was an option, and also stock on the Super BP’s and 1500XS. The boat was rigged with a dual opposed rack and pinion ride guide steering system. The secondary steering cable tube is hard to come across, as well as the linkage arm setup. There were also the optional checkmate trim tabs on this boat. It was really cool to see an Action Marine sticker on the motor as well. Many performance oriented Checkmates came from Action Marine.

I wasn’t actively looking for another boat, but I came across this on craigslist during my routine search for parts. Even with assuming the motor had low compression, and the hull was totally rotten, it was a good deal. I was in need of a trailer still. Although quite ugly, and a roller, this trailer looked solid and would suffice. I was also lacking the dual opposed steering linkage arm setup. I had been watching the later model short mids and louvered cowlings rise in value, so I figured I didn’t have to worry about getting my money out of it.

At this point, I was still planning on using the 1350 powerhead with the Super BP mid, but I was likely going to be tempted to borrow the louvered cowl off the 1500.


Also, just want to point out that this MX-15 hull is for sale with a trailer, without any titles or registration. Feel free to send a pm if interested. Assume new stringer, floor, transom, and paint job are required. I also have a running 1969 Merc 100hp short shaft and spare 68 100hp powerhead I could sell with it.

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[tnelsmn]

Thats a great buy for that inline!

[starviper10]

At this point, the structural rebuild of the hull was almost complete. There was just some tabbing to add, and the front bulkhead to build. The bottom was in pretty rough shape with lots of scratches. The deck had a lot of holes that needed to be filled, and although the dash and the deck stringers were not rotten, I wanted to replace them.

I started to think about some of the big decisions I need to make before painting it, such as the seat design & locations of the throttle, steering wheel, gauges, battery, trim pump, fuel tank, etc. I never had a small outboard powered boat like this before, or ever even driven one, so I was in new territory. I didn’t want to make any haste decisions that I might get stuck with and really regret later. I was fortunate to have a summer internship close to home, so I was home for the summer and therefore able to resume working on the boat. I decided to take the summer to get the boat running and out on the water, such that I could start playing around with locations of components, and get a feel for the boat. After spending some time driving it, I would then tear it back apart to prep for paint.

Step 1: Splashwell Repair
There were 10 holes in the splashwell that needed to be filled in, including the big cut outs for whatever genius put the transom bracket thumb screws through them. I also built the area back up where the transom cut out was. My repairs weren’t perfect, as there would definitely be some more work required before final paint, but all the holes were sealed up now.

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[starviper10]

Viper1 (Sammie from Action Marine) over on the Checkmate forum gave me tremendous amounts of advice for this boat, including trim positioning. I attached a screenshot from my CAD model of the correct dimensions that utilize the strake corner as a datum.

After drilling the holes and bolting them on, I noticed that they didn’t sit flat, and had large gaps on the outer corners. There was a slight angle in the transom a couple inches above the bottom edge that was the cause. My solution for this problem was basically a fiberglass spacer/adapter that would sit flush between the trim tab and the transom, with a tapered corner. I glassed 7 CSM sheets together, then grinded it to fit as best I could. I then used some duraglass to fill in any large voids that might still be left.

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[starviper10]

The transom bracket was likely the component that I stressed over the most. As you can see by some of the pictures in Post #1, I have put the boat through some rough water, giving it a decent structural test. However, this is still something I worry about, and I would appreciate if anyone has any suggestions as to whether it is sufficient or needs more reinforcing.

From what I’ve gathered, these hulls don’t do well with setback. Combine this ideal 0 setback with my goal to have a period correct restoration, a simple transom bracket seemed like the way to go. The MX-15 had a simple single piece steel sheet bent to form a U shape. It dropped right on top of a block of wood sitting on top of the transom. I wanted to make something more professional looking. I drew up some designs in CAD, matching the side edge angle with the trim tab angle.

Another design decision that I would appreciate feedback on is install height, but I’ll speak to that in a later post with pics of the engine installed. For this post, I’ll just explain the construction of the bracket.

Looking back, I likely should have simply made the transom higher with transom knees extending upward through the splashwell to negate any need for a bracket. After all, the splashwell was swiss cheese anyway with all the holes and cut outs. However, at the time of the transom install I was trying to keep the boat looking original, so this is what I ended up building.

The bracket is comprised of 3 main parts, 2 plates and one welded element. The 2 plates are 7075 T651 0.25” AL that run vertically on the inside and outside of the transom. The inside plate extends as far downward as possible before bottoming out on the splashwell. Finally, a welded 6061 AL rectangular stock structure is sandwiched in between these two plates. Note that the T-handle thumb screws land roughly halfway down this structure, so they are no longer clamping on the wooden transom, which where my concern really stemmed from. However, they do land on vertical sections of rectangular AL stock.

As for bolting, there are 4 bolts that hold just the outside plate onto the transom, the top 2 of which also bolt through in the inner plate. There are 6 additional bolts just for the engine. The two engine bolts at the bottom landed at the transom crossmember height (crazy long 8” bolts). The top 4 engine bolts go through both vertical plates and the power trim brackets, 2 of which land low enough to hit the wooden transom, which made me feel a lot better.

I likely went excessively far down with the outside plate. I might trim that up some, maybe equal depth to the bottom of the trim tabs. I hate the idea of filling in holes on a new transom, but the depth of that plate bugs me.

Also, please excuse the galvanized bolts in these pics, they are what I had at the time for mocking things up.

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[starviper10]

Other than dropping the powerhead onto the mid and mounting the lower unit, there wasn’t a whole lot of work required to get the engine running. The Super BP mid required shorter length powerhead and lower unit studs in areas. I was afraid of the lower crank seal going bad and letting air in, so I replaced it while I had the powerhead hanging.

I was surprised to see that the trim cylinders did not align with the mounting brackets. A quick measurement on a stock short mid reveals that the BP mid’s lower shock/trim mounts are ~1” wider than stock, likely to account for the added width of the mid section. I didn’t want to cut up perfectly good, stock trim rams, so I simply flipped the lower mounts around 180°, and later added washers to account for the difference.

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[starviper10]

The next step was mounting the engine. Yes, I did make it such that steering cables cannot be replaced with the engine mounted. I didn’t plan for that, but with the additional height of the transom bracket, the splashwell walls were too low. I know one solution is to drill vertically downward on either side of the splashwell and use some chrome vent bezels, but I would really hate the look of that.

The transom bracket adds 3.5” to the 19” stock transom for a 22.5” grand total. Given this transom height, I believe that the prop shaft should have ended up ~1” below the pad. However, the thickness of my transom bracket caused the engine to rise another ~1/8” due to the rounded corners of the transom clamp brackets (I added a ~1/8” strip of AL to alleviate the point loading on the clamp bracket fillets). This places the prop shaft ~7/8” below the pad.

Anyone here run a similar install height on a similar hull? I have yet to have any water pressure issues, but I should note that I have only ever ran with a 1500XS lower unit. One concern I have is if I ever damage the lower unit past repair, and if I can’t find another one, as I’d have to run a stock lower unit. I’m not sure if I’d have sufficient water pressure at this height, even if I plug the upper holes.

I’ll skip forward a little timeline wise briefly to when I had the boat together and running. Performance wise, I was just around the 60 mph mark with a 28p small ear chopper at full tuck. The engine has good compression (135 psi across all 6), but the hull does have quite a lot of scratches, some fairly deep. I didn’t trim up much at all, as I was a little apprehensive without having the boat more completed. I also have 0 experience with chine walking. Unfortunately I never got a tach that worked to know what rpm I was at. Looking back that was rather foolish not to prioritize that while I had it running, as slip numbers would be very helpful.

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[1954bmw]

Really surprised you could spin that 28 pitch, I think on my MX15 with a 135 on a homemade jack plate, I had a 22 pitch chopper that ran right at 59/60 mph.

[FMP]

Great thread, super details.

[starviper10]

I finally got the boat running and in the water on August 19, 2017. It was a totally new experience for me, driving a boat that required full throttle to get on plane with some delay. I was actually a little precautious in that I didn’t commit the first couple of times, as I was afraid something was wrong. On the 3rd time I put all the weight I could forward, just hammered down and sure enough she got over the hump and took off. My dad was driving our Ski Nautique as a safety chase boat, and it was quite thrilling to pull away from him, as he topped out at ~40 mph (straight inboard).

However, my first joy ride was short lived, as after just a couple miles the motor started to lose power and die. My dad had to tow me the rest of the way home. I was guessing it was likely fuel related, and sure enough the fuel filters on each carb were dirty. After some cleaning, running a direct line straight to the pump (removing quick connect), and using a different tank, she was back up and running. I had a blast driving that boat for the rest of that week. I had to pull her out of the water on August 26 because I had to head back to campus the next day for my junior year of college. It really killed me that I only had a week to enjoy it. I was able to swap the boat to the MX-15 trailer, which is a much better trailer, albeit a rather ugly color.

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[starviper10]

I had a rather spontaneous decision to put the Checkmate in the water when I was home for Thanksgiving break, as the weather was decent, given the time of the year (low 50’s and sunny in northern IL). Since I last ran her, I had also purchased another small ear chopper, a 28p (I only had a 24p until this point). Here you can see how much wetted hull I was running, as I had no trim pump installed yet. At this trim position, the 24p put me around 55mph, while the 28p got me around 60mph.


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[1954bmw]

And, is it done??