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View Full Version : Jackplates and a few other questions



JSB5776
04-14-2002, 09:37 PM
OK guys... by some fortunate... or possibly unfortunate (if you actually saw it) twists of fate... Ive come across an 80's 16' checkmate predictor... interior destroyed... It was left uncovered for 4 years... but the Hull seems solid... and a 1996 150 HP merc black max with a cracked piston.... and in a little transferrance of aluminum on to the walls in another cylinder... So I guess what Im saying is that I would eventually like to mate these two currently non fuctioning pieces in to a fast little boat... Im completely new to the outboard world... but have been boating for years... So I would like to ask you guys a few questions... First... the predictor is rated to 125 HP... but everyone I ask says that the 150 will be fine... just dont hammer the starts all the time... Will the 150 be too much for it??? Second... what do Jackplates do??? and do I need one... It seems everyone is running one??? would one be benneficial in my case... and third... Does anyone have any info on predictors??? history, weight, or just anything interesting on this model that I would like to know??? I do searches for predictors... and all I really ever get is a classified on someone selling a 22' predictor... but very little on the 16's... Ok two more questions... What does it mean to "Blueprint" a hull??? Ive read some threads about flipping the hull over and blueprinting it??? what do you actually do to it??? and finally... Can anyone give me an estimate of an approximate top end with the 150 on it??? Thanks for all your help... and Im glad to be stepping over to the performance outboard side of this hobby...

Jeff
Saratoga Springs NY

pyro
04-17-2002, 09:03 AM
Welcome!

Nobody else replied, so I did to put your thread at the top...

Check the hull over closely. If it was left outside, it may have some hidden damage. A lot of the Checkmates were very well-built, but it still may need some serious attention. Check over the flooring toward the rear, under the gas tank, back seat frame, etc. Even if the floor is solid, it still may have a rot-soaked transom and stringers, you can't tell unless you tear up the floor.

What year is the boat?

The 150 is decent power for the boat. If the transom is solid, it will hold it just fine. you DO want to go fast, right?

A jackplate can do two things: Its main function is to place the motor higher on the transom, to reduce drag. In some cases, it is raised high enough to use a surfacing prop, requiring the use of low-water pickups.

Blueprinting a hull means to true all of the running surfaces, to make the boat bottom "perfect" shape, it can achieve its full potential.

I've never owned a Checkmate, but there's lots of C'mate guru's on this board who can help you and maybe estimate what to expect from this hull.

-Chad

AnthonySS
04-17-2002, 09:49 AM
I am a concernd about 150 V6's on the back of most 16 foot boats..regardless of the make.

Fisrt of all the 1996 Merc is HEAVY motor which is going to make this boat porpoise severely in the mid range. The boat will literally have to be driven slow or fast and not much in between.

Also I think the WOT capabilties of the 150 will exceed the boats threshold of Safe drivabilty,

SORRY...don't mean to discourage you...but I would fix up that V6...sell the checker and look for a Vector/Vking type hull or even a Tunnel to put that 150 V6 onto if you want to go fast safely

Checkmark
04-17-2002, 12:58 PM
I've seen Predictors around with 115 or 125ish Merc inlines or OMC power. The V-6 will work, but only with the proper setup.
Checkmate is known for over engineering their transoms. If it
hasn't soaked water, it should handle that engine with some
stiffener plating across the top and bottom engine bolts.

If I remember right, the Predictor weighs around 800 lbs, so I don't think with the 375 lb weight of the V-6 you will need more
than a 2" setback; like a land and sea jack gives. The V-6 adds
approx 80 lbs over the above mentioned engines, so I don't see
that as a big issue. The power is what you need to control. A jackplate will allow you to lift the engine and gain control over
chinewalking that can occur due to to much gearcase in the water.
You should also consider a nosecone for the gearcase, with low
water pickups to control prop blowout at high speed, and feed
water to the heads when the engine is lifted. A No Feed Back
steering system from teleflex, and solid motor mounts will also
enhance safety and driveablity at speed.

This combo will yield 70+, but it won't be safe in any kind of big
choppy water. Just remember to trim in when you see any sign
of waves!

AnthonySS
04-17-2002, 02:19 PM
Checkmarc

Sorry...

I don't generally debate things here but...

why would you recommend a Nose Cone LWP on a 70ish mph boat.

I think your post promotes spending money on a potentially risky set-up....wouldn't it be better to promote a V4 / inline setup as you started saying in your post??

Also you said...

"If I remember right, the Predictor weighs around 800 lbs, so I don't think with the 375 lb weight of the V-6 you will need more
than a 2" setback; like a land and sea jack gives. The V-6 adds
approx 80 lbs over the above mentioned engines,"

I am not sure what the above means...I believe most V6 150 Mercs, except the XR6 were rated at 404-410 lbs. Did you mean V4's weighing 375 lbs?

Does Land and Sea make a 2" Jack Plate....I thought they had at least 4" of setback on thier Model 600...or did you mean 2" spacers???

Anyway I would love to here your additional thoughts

Checkmark
04-17-2002, 03:01 PM
I'm giving Jeff my thoughts on how to make what he currently has
in mind, work. If I thought he was clueless and out to get himself
killed, I wouldn't have replied, but since he has been around boats, and I happen to have experience with Checkmates and
other overpowered boats, I gave my input.

If he has potential to run 70+ which he obviously does, he stands
more of a risk of blowout with the stock gearcase than he does with a nosecone. He also needs the low water pickups to raise the engine. The added length of the unit will help with control also. What have I said that is false?

I own a Land& Sea hydraulic with 2" setback. I also have a manual from merc that states the 150 as weighing 375lbs. A
Johnny 115 I worked on, weighs 315 plus the pallet it was laying
on.

Anyway Jeff, I think you can make a nice lake rod out of this combo. If you get a chance, bring your rig to Oneida Lake this
summer so I can check it out!

JSB5776
04-18-2002, 09:52 PM
Ok guys... thanks for your help... Ive been ripping this boat apart and the transom seems solid... Im gonna pull the gas tank this weekend... and see what lies beneath... The 150 merc is 404 #'s... which is the same weight as the 135... and not much more then a 125, which is what this boat was rated for... I have spoken with a the guys from an excellent engine shop in Lake George NY... Incase your wondering, they built a 160 MPH skater that was featured in HOT Boat... Seriously, check this link out...

http://free.hotboat.net/hbcove/28/1/index.htm


They say the 150 will be fine... but seeing how the most stress a transom will encouter is on the start... just not to give it full throttle outa the hole... Once your up and running... the say there shouldnt be a problem with stress on the transom... OK... couple Questions...

AnthonySS... You think the extra weight could cause porposing in the mid range??? would there be any way around this??? and what are we talking midrange??? 40, 50 60 mph???

Checkmark... You mention "blowout" at high speeds... I currently own a 21 foot searay cuddy... with a 260 merc that does 46MPH... so blow out is not in my vocabulary... Could you enlighten me a little???

Also I see some guys running 10 or more inches of set back on certain boats... how would you know.. before hand what the proper set back would be.. and can you get a jack with a wide range of adjustment??? or do you need to buy one with a certain setback inmind already???

Yeah Lake George is a 32 mile long lake, 2.5 miles wide at some points... we can get 4-5 foot swells, or have glass... it changes daily... so I know Im not gonna be running this thing period.. let alone fast in bigger water... but for those calm evenings... I wouldnt mind hitting 70 every now and then... as long as this thing doesnt tumble on me...

Thanks again for all you help guys...
Jeff

AnthonySS
04-19-2002, 08:44 AM
Dear JEFF,

Yes I agree that your 1996 150 is 404#. 150’s where about 378# back in the mid 80’s. You are forgetting something though. Your Boat was rated for 125 hp when 125’s where in only available as V4’s and inline4,5 and 6 models. Those engines weigh quite a bit less then 1990’s V6 Power plants of similar HP.

I am not try to say that you won’t be able to have fun with this boat with your 150, and I know Checkmark will agree that set-up is key. I just don’t want to see you spend tons of dough on something that could be a real handful…if set up with Jack Plates, LWP, nose cones etc.

Without question…with all the go fast items you have a potential 75+. I just don’t think the boat was safely designed to go that fast!

Wait till you see what happens when you hit the slightest wakes or have to slow down real fast with this boat at 75 mph. HOLD on…and make sure you have a safety lanyard, foot throttle, remote trim, solid mounts and GREAT dual steering!! Again this will add cost to your rig if it isn’t already equipped with such items.

Also if you add the jack plate…You may need to add extra length steering cables.

If your going-up on the jack plate…,start looking for a Surfacing over hub SS prop.

Make sure you find a prop with medium to low rake…cause the steering torque will be heavy. A lower Rake prop will help reduce steering torque. Also make sure if you do the nose cone that it also has a toque tab. Again this will also reduce torque steer.

When coming off plane watch out for following stern Wave. With all this mass hanging off the transom, and if you have passengers in the rear, it will take on water. This can be alleviated by “burping” the throttle some, just as you see the wave coming, or even turning the boat, again when you see it coming.

Yes most Short Boats (17’ or under) with short keels will porpoise with a 400# V6 on the back in the mid range. Some times no mater what you do it will always be there…I would say it will do it between 30 and 55 mph’s. This is mostly due to the mass hanging of the transom on a short keel boat.

It won’t go away until the boat is up and flying. I cannot remember if your Mate has a pad (Maybe a small narrow one?,…Checkmark…please advise). If there is no pad…this boat will want to chine walk quite a bit!.

Anyway if you get this all set-up and you have issues with chine walk, we can spend more time with set-up and driving techniques to handle in the future.

Again, I don’t want to discourage you or Checkmark on what you may think this boat needs. However Please be aware of some of things to consider. In my opinion…it is a lot of money that would be better spent on a hull more suited for a 150 and all the Go-fast goodies. This is not saying your “Checker” is not a good boat…Just saying it will have limitations if you add all the go-fast stuff.

If this was my boat and I was bent on having that 150 on the back, I would set it up to just be a decent ski-pleasure boat, optimizing set-up for 70 mph and under mark. Then you will not have to contend with issues like Blowout.

By the way your standard V6 Gear case should be good for 80 mph (or more) before having to worry about blow out. Blow-out is another area you don’t want to go. If you want to read articles on it here you go:

http://www.pbcc.on.ca/main/Blowout1&2.html

If I was bent on all the Go-fast items, then I would be looking at a different hull.

Hope this helps more!

check88
05-14-2002, 04:44 PM
hey jeff,sorry to be getting into the discussion late but i had a predictor a few years back with a 115 merc on it along with 4" of setback and what anthony is saying about water coming over the back is very true.if i had any more than one other person in the boat with me and i slowed down too fast i would get a huge wave over the back of the boat all the way over the back seat!soaked my sisters more than once in that thing.if you do decide to hang that 150 on the back i would say to use no setback cause that much weight should be more than enough to counterbalance the hull.maybe play with the height on the mounting holes.i know mine ran about 65 mph with just me and almost out of gas but it was a handful to keep it from chinewalking at those speeds.almost got tossed out of the boat on more than one occassion.definately get solid mounts,dual steering,kill switch,foot throttle,and a good life jacket when you first take it out to get the hang of it.good luck with it.

Toffen
05-19-2002, 10:06 AM
Hi!

I need some matematic help here:

I have added a 2 inch CMC spacer between my Promax 300 and my 5,5 CMC powerlift. When using the CMC lift only, the sweet spot for my blueprinted Tempest (propshaft) was 2,5 inches below the bottom.

Where should the sweet spot be now?

@ 2 inch more setback +
@ the spacer imply a lower mounting of the engine since the transom has a negative angle of 15-18 degrees.

If I am correct, the water will hit the propshaft 0,5 inch higher due to added 2 inch setback. The propshaft will be 0,66 inch lower due to the spacers do not compensate for the negative angle of the transom.....

Roughly I have to jack the lift up 1 inches more to reach the sweet spot...... or?

Any ideas?

Cheers, Toffen - Norway

Techno
05-19-2002, 12:19 PM
Toffen, I think you only need to go up about a 1/2 Cm or so. 1/8" -1/4" for every inch back. It's not hard math but a general guide.
Thats why you have that powered jack plate, to play with it.
I see what your saying about the angle of the transom but it doesn't matter if your using the bottom as a reference point, it doesn't change. The water is rebounding a little more and your moving your fulcrum and weight back more. So maybe 2" below the bottom?

JSB5776, A couple things that weren't spelled out. The blueprinting is making it flat and true for the last 4 or so feet. & making the edges sharp Especialy at the transom. Rounded edges add drag and the biggest one is the transom/bottom edge. But the rest do too. Its only needed for the part of the boat that sees the water at speed. Thats why the short length. Some boats have a designed in hook or lip on them and usually shouldn't be removed.

The hydraulic jack lets you tune while you go and a manual lets you tune but you have to stop and do it. This is for hieght of the prop in relation to the hull bottom. The set back changes the fulcrum of the prop at a trim level, like a longer lever and it changes the boat balance.
If you run like 5* positive trim your wasting thrust in holding the bow up. By moving the engine back you change the balance. The trim can be reduced because it has more oomph to it because of a longer lever on the boat. Less trim angle means more thrust in a straight line, more speed. The big advantage of an outboard over an inboard is it allows you to change both of these items. Even without a manual jack plate the OB can be moved through the choice of mounting holes on it.

A hydraulic jack also lets you bury the prop for sking or getting on plane and raising it later. Its like having power trim but vertical instead.

My boat has a built in setback, so it doesn't need one. A lot of people run one anyway. If I can take my plate off I'm going to try it without it this year. So I'm turning right while everyone else is turning left.

Your boat will probably feel fast at below 70 speeds by what already has been said. Its a reletivity thing. If you can't reach 70 it won't matter much, its still fast.

glossary (http://www.screamandfly.com/screamandflymagazine/Speed%20101.html)

Checkmark
05-20-2002, 07:24 AM
I don't mean to get off the subject, but I am interested in your opinions on your built Tempest. I am in the market for either a
Trophy or a Tempest, or both!! Would like to know if the Tempest
is a good top end prop, or if I should look to a Cut Chopper or
Raker or whatever. Thanks for any input!