View Full Version : STV SETUP with SM Gear Cases?

06-20-2001, 01:57 PM
STV Setup with SM Gear Cases

Dear STV-Owners,

Some of may know that after an unfortunate incident at F2K my Bobs Drive was destroyed. Therefore , by the Grace of God, I now own a SM gear case for my STV PCS with MPP 2.4 EFI.

Well after only 2 hrs use last season with the SM, it revealed some ugly traits that made me feel like a rookie again. Since I ran the Bobs drive consistently at above the Pad, I immediately put the SM to as most say they can run higher then the Bobs.

With a load in the boat the SM gear case felt spot on running easily to 95 mph+ with 2 aboard. As the fuel load got lighter, the boat would not produce any lift and looking back at the stern, the stern was visibly lifting out of the water , the spray off the prop was huge, and the engine had severe torque with major crab angle. The Boat was virtually undrivable, like it was running partially blown-out. RPMs were around 7K with speed at 80 (really inefficient) By the way I am running a 14 x 30 cleaver prop.

It seems to me that the SM is mounted to low and it is literally planing the stern of the boat up and restricting the boat from getting any bow lift (stuffing the nose down).

What are your thoughts guys? Anyone else had this problem with the SM on STVs

I know most of you, like RT, think I should go higher and be able to run about 1 above the pad.


Anthony SS.

Damage Inc
06-20-2001, 03:53 PM
By no means am I an expert on the subject, but maybe you should try running a "bow lift prop" rather than a "transome lift prop."

I have two friends with STV's and the Hot Boat Magazine prop test on STV's, and all say the 14 1/2 X 27 SRX is the best all around prop for that boat. BUT, they are both using a Bob's nosecone, so it may not work as well for your set-up.

Maybe something to think about, like I said, I am no Guru!


Michael Dixon
06-20-2001, 05:56 PM
I agree that nearly all gearcases drive better than the sportmaster and I probably wouldn't run mine if it weren't bulletproof. My suggestion is to try it at 1.25 above the bottom. That's where I would start anyway. By the way, which bottom do you have? I will add that I never did set up my light boat to sucessfully run the SM. Sportmaster seems to add hop to an STV and some ill handling characteristics to a light one. It runs flawlessly on my Euro because of the extra 300 pounds of boat. If your boat is fairly light, it could be actually riding on the gearcase. As long as you don't have a shortened skeg and have water pressure too high usually isn't a problem(no more than 1.75) Good Luck

06-20-2001, 05:57 PM
I agree with both suggestions the guys have made to you. #1. Try a different prop. My buddy had a little liberator back in the day and the only prop he had was a cleaver. You talk about a hand full. That cleaver would lift the stern completely out of the water and that little boat was scary enough. I know their expensive, but try a ET. A yamaha or RE3 might do the trick as well. #2. I think you could go higher than 3/4" above the pad. I know it's not the same boat, but I run my CLE on a Mirage 1" above the pad and it runs fine. It is a modified CLE, but my point is, you should be able to run that Sportmaster that high and higher with no problem.

Mark Screen

06-20-2001, 05:59 PM
Anthony, lower it down to even with the pad and let us know what it handles like. I remember a post by a cat driver a few months ago that had the same problem, his problem cleared up by LOWERING the SM case so that the lower half of the case wasn't 'planing'.

06-20-2001, 07:24 PM

MY PCS is a 1992 with the SKI Bottom, It weighs 775-800 lb. and I agree that I also want to use the SM cause it is bullet proof!



06-21-2001, 06:15 AM
I can't offer much input on anything else other than the SM case because that's all I have owned. Only getting into my 3rd year owning a STV but this is what I can offer. Last yesr I purchased a ET28 and CMC 5.5 plate because of poor luck the previous year with RE3 and SRX props. The boat just didn't feel right above 85. With the propshaft set at 3/4 above the pad the ET28 along with one person would run great. Add another person and boat starts to propoise at 85 and will not stop. With propshaft set to 1 inch and one person I have the same problem. Want to try and go higher just to see if it goes away or gets too crazy. Last year I had the chance to try a bunch of lab offshore cleavers and they all were the best prop to run above 85 with one or 2 people. Prop shaft was at 3/4 above pad. Last time I checked water pressure was close to 20psi so I think with the cleavers I might be able to go higher someday but get worried about loosing control since I am still new at this HiPerformance boating thing.

AnthonySS, if you ever get that video on CD to run it shows the Euro running with the setback and propshaft at 3/4 above pad.

[Edited by Euroski on 06-21-2001 at 06:34 AM]

06-21-2001, 06:28 AM
Maybe I shouldn't post an opinion, because I haven't run my STV's with both heavy and light loads, but I have run both Cleavers and RE3's on XR6's, Sportmasters, CLE's/stock, and CLE/Bob's, as well as SSM's. I don't even have any idea where the transom height is on either boat. I've always set um up where the rooster tail is lower than the top of the engine at close to top speed. I've always thought the cleavers are the best all around blades on STV's. I've also always thought a little lower is better than a little higher. When I had a Mirage with a SSM gearcase, it also had a hydraulic jackplate and a trim and height guage, so fooling with the transom height was a lot easier. Even with the SSM's almost no torgue personality, the boat would feel loose, crabby and rooster with just a little too much height. I did run this boat once with a big gearcase too and had about the same outcome, never did see going up more as the answer. Only props run on either gearcase were cleavers (stern lift) I'd drop it a little and try again. I've seen other people who thought they had boat planing on gearcase problems, but I've never seen it myself.

06-21-2001, 10:29 AM
Hi Anthony

as a soon to be pro comp/2.4 EFI owner with a sportmaster and a 30 cleaver (yes I sold the Triad), I will be able to say for sure what the deal is.
But what I can tell you is something is up, 25% slip?.
I would say go up, we have always run our sportmasters as high as possible while still retaining good water psi. I do not like the feel of the boat with a low motor. Keep in mind that we are looking for top end, and that if you were to drag you would run a different setup. All the STV's I have run never make it into positive trim.
Remember that with setback you have LESS bowlift when running a cleaver. The setback give you a mechanical advantage, it works bothways.
What I can say for sure about the sportmaster is that it does need to be run higher than the CLE or bob's.


06-21-2001, 10:53 AM
I just read my post and realized I should clarify the setback thing.
The setback is a mechanical advantage, it can drive the bow down with lift from a cleaver, because it lifts harder. If you were to run on the transom with the cleaver you would have more bowlift than you do now with the setback.


Michael Dixon
06-21-2001, 11:03 AM
Anthony, I totally agree with firewalker on raising the gearcase. It is true that if you lower it enough it will handle a little better than you are now (mainly because you'll be running 10 mph slower and if it is low enough it can't plane off on the gearcase. On the other hand if you raise it to 1.25-1.50 (center of propshaft to bottom of boat) it should drive fine. The reason I asked about weight was that a lighter boat would be quicker to ride on the gearcase. Again I agree that if you have water pressure, you can't get to high with an unmodified sportmaster(which usually is less than 2" : I prefer 1.375) Good Luck

06-21-2001, 11:54 AM
Thanks for all your comments. I think I will start by going up...That's what a figured as I can't imagine putting it lower as I think 1/2 - 3/4" is already pretty low.

This is also why I was aking about measuring transom height. I want to make sure the SM is in the 27"-30" transom height as recommended by merc. I realize too with the 5.5" of setback, I might be lower then I think!



06-21-2001, 10:11 PM
I hope you'll post results after you go up. You and Rob have my curiosity up.

06-22-2001, 12:14 AM
Anthony, I am running the sportmaster as well as you know and it sounds like you are having the same growing pains. Only difference is you have had more experience.

As you know I am running a 28 ET on mine and it seems to work very well. (I have about 4" set back) I think with the additional power you have you could power through the bounce I have at 85 and the ET would work well for you.

I am lifting the motor this weekend and am going to try a 27 pitch spinelli prop and a 29 SRX OMC prop. I'll let you know what they feel like.

Keep in touch.


06-22-2001, 05:34 AM
Let me know how the SRX worked for you. On my Euro it had a "ton" of steering torque and felt like the hull would "hunt" above 90. Just as if the back of the hull would be wobbling back and forth. Glad to know my ET28 acts the same as your at 85...

06-22-2001, 09:03 AM
...tell us more about your STV? Model, Hull, Hp etc.



06-22-2001, 10:37 AM
Anthony, I just got word from Blake that the Pro Comp ran 114mph on GPS with a 14 3/4 X 30 Merc cleaver (it is a 15X30 that was cut down by mercs lab.)It was bolted to the transom in the middle bolt hole with a stock sportmaster, running 30lbs of water psi at 7950rpm.
What is astonishing here is it has about 5% slip(we are not 100% on the tach, or have we put the prop on a pitch gauge)but none the less he said he was very very pleased with how the boat ran. He also stated that it had great acceleration, no steering torque, and felt perfect. This was with a 100% stock 1990 motor, on a 1992 Pro Comp.


06-22-2001, 12:05 PM
Dear ROB,

That's impressive! It's amazing what a 2.4 can pull. That's got to be the fastest STV with a 240 around. I'll be happy just to get a nice handling boat back that will run an honest 100...

I am on holiday next week so I'll hopefully get a chance to play some! ...but got to get my dock finished first!



06-22-2001, 12:46 PM
Blaine Schells Pro Comp is/was the fastest 2.4 powered I have everheard of. He has since moved to 2.5 power after his last set of weisco pistons only made it 5 miniutes, into breakin before they chucked a locating pin. (I know weisco's are junk, but that has to be a record).


Michael Dixon
06-22-2001, 03:20 PM
Anthony, I run a light weight Triad STV river rocket with a ski bottom(496#) with a modified drag motor, XR-6, and usually a 32 cleaver or a 26 hackney. My favorite is my other boat : Triad STV euro with a mod VP bottom with a modified drag motor, sportmaster, and usually a 29 Mazco re3. I don't prefer this gearcase, but is nice not to have to worry about breakdowns. I plan on testing between XR-6, sportmaster and Bobs nose cone this weekend as well as several different props. Let us know how yours handles after you raise the motor. Good luck.

06-25-2001, 08:26 AM
Tried the 29 SRX this weekend. Took it out Friday, there was about 6" chop with a good tail wind. First run, speedo read 90, rpm looked to be about 6300 and aired out perfect, no bouncing. Thought this was the prop. Ran at slightly negative trim. This prop revs up to about 4000 rpm and comes on plain versue the ET that revs up to 6200 before planing.

However, it was calm most of the weekend and the bouncing is back. It will run consistantly around 85 (with one or two people) while bouncing but it is not really enjoyable. Didn't have a chance to raise the motor yet but I think this is the next step. I was comparing the spray with my buddy's Euro and I am definately too low. The center of the prop is about even with the pad.

Seems like I can't get the back of the boat out of the water. Even with the 4" set back, lift in the front is no problem.

27 pitch Spinelli prop was not good.

06-25-2001, 02:37 PM

Just what I like to hear...a happy family of STV's. I would like to have 3 myself.

1. My Boat STV PCS
2. A mod VP 2 Seat
3. ..and a EURO

Let us know how your testing goes too!

Why do you use a 29 RE over a 30 Cleaver? I tried a 30 RE once and claimed the prop to be overated as it made the boat want to roll and fighted me at the wheel!



Michael Dixon
06-25-2001, 03:34 PM
I have two re's: a 28 and a 29. My 29 performs better than any prop I own. (with the exception of overall top speed which goes to the 32 cleaver) My 28 is a dog: out of the hole, midrange, and top end it won't run with my 29 or several of my other props. I guess I just got lucky with the 29. Weather stopped testing for the weekend. May test this week sometime. I did get to run the bob's nose cone with a few Mod vp changes and I guess the sportmaster will get parked. I haven't checked overall speed (which I'm sure it'll be faster anyway) but drivability is awesome. There is no bounce, no crabbing, and it carries the boat with perfection. I'll let you know on the testing.

06-25-2001, 04:41 PM
Know what you mean by the back of the boat is "stuck" to the water. Mine feels the same way with the SM/Merc ET28 combo especially when I add another person. With just myself it works great. Went through the Mazco's RE's and SRX's and none worked well for me. So far the ET and Lab cleaver I tried last fall work the best. Ordered a new Merc lab and with luck should be here in a day or so to try out. Talked to Merc lab department and had some time to chat about the ET, they siad the way the ET is designed it has a tendency to suck the back of the hull down. And, from chatting I got the idea it was more so on the sportmaster.

Hey havin fun anyway.

06-25-2001, 09:29 PM
Yeah I loved the Bob's Drive it was like bolting on power steering, However they don't hold up, I got about 60 hrs out of mine before the skeg failed...

Keep an eye on the skeg!



Michael Dixon
06-25-2001, 10:48 PM
Thanks for the warning. I just sold a 2 hole cle to a guy with a stv sprint boat that had just broken a skeg at about 85. Luckily it wasn't a bad deal; but it defenitely could have been. Right now I'm chasing water pressure problems with my bobs lower unit. Have replaced every gasket and housing in it to no avail. I put the sportmaster on and will check it tuesday. Hopefully its a powerhead base gasket and not just my best gearcase. About props, for just cruising I like the et's too. Mainly for the bow lift. Again thanks for the skeg warning.

06-26-2001, 07:55 AM
Mike, I never had much water psi with my Bob's modified case. As a matter I don't think I ever even got 10 psi.
I too, have run CLE (two and 4 hole), a CLE modified by Bob's, a stock sportmaster, and a Mod sportmaster. I for one, am not a huge fan of the Bob's. It is supposed to be faster than the Bobs, but I have never liked the way it made the boat feel. The one thing that the Bob's drive did do nice was go straight. I think that the bob's / cle mod case is far better than a 200/bobs as the skeg is full and a lot thicker. Not to mention the propshaft and carrier.
I am a sportmaster fan. But it did take awhile to make it work right. My reasons are that I haven't broke one, it handles well, it is real fast and I have never blown out with it, I cannot say this of any other case.

Just my two.


Michael Dixon
06-26-2001, 10:15 AM
Firewalker, was 10 pounds enough to cool the engine? I had just run the bobs before I had a friend modify it and I'll agree that until he worked it it drove a little funny. I think that it is a cle with a nose cone. My only complaints with the sportmaster is the extra hop and it doesn't seem to "tote" the bow as well. Now that you mentioned it, its the only case that hasn't blown out with me at some time or another. We usually cruise the river at about 60 - 70 and that seems to be where the hop starts with the sportmaster. As far as WOT it does fine. Any comments on gaining water pressure with the bobs nose cone? Thanks Michael

06-26-2001, 11:22 AM

Mercs recommended transom height is from the bottom of the pad to the top of the transom, and tells dealers what motors can be used on what type of boats. It is sometimes used by boat builders when they are designing a boat that they want to be able to use a particular motor. Like when the 300 promax came out. several builders built hulls specifically to use this motor, and one of the dimensions that they incorporated into their hull design was the "recommended transom height". It is completely independant of propshaft height above the pad.

06-26-2001, 03:46 PM
For the bob's case I never had good water psi. But it was explained to me once that if you have psi and it is not steam the block is full of water. If it is full, you cannot squeeze more in their, so it is cooling as much as possible. I never had over 10psi, more like 5-8 and never lost a motor. My Sportmaster now runs 30psi. Also I have always felt that the sportmaster was the freeest running case on my STV's. It also has never blown out, and at over 125 that is some thing I really like, easy to maintain to.


06-26-2001, 03:51 PM

reminded me to open up my Merc Service Manual and read the section most of us skip over cause we have done it so many times....INSTALLATION

There is a diagram there (that I knew I had seen before) that defines Transom height and shows the reference dimension. I just want to make sure I am in the 27-30" range for the SM case!

Thanks Again,

I hope to get out some time this week!



06-26-2001, 03:54 PM
Anthony, I am kinda wondering why you are interested in the merc spec?, I would expect you to be outside that range. I don't think that trying to make it work in the 27-30 area is gonna work.
Just curious.


06-26-2001, 04:54 PM
Just got done installing the new 14.5x30p lab cleaver and heading for the water now. Wondering, my ET runs best at 3/4-5/8 inch above the pad with 5.5 setback. From experience where should the propshaft be for a cleaver?

Also note for anyone ordering that mine came with the hub for the newer 1.25 inch shaft. Lucky I have the hub from the ET.


Jim S
06-26-2001, 07:08 PM
the new 1.25 hub please e-mail me.
Thanx, Jim

06-27-2001, 09:44 AM
Here it goes, how are you guys measuring motor height to within 1/4" increments? What is the best way to check what height you a running? I leveled out my motor, took a straight edge from the bottom of the boat to get idea of where I am at. From this, it is still kind of a guess. What's the best way to do this?

Jay Smith
06-27-2001, 10:34 AM
Pro comp.
We take a boat and level the bottom of the pad by using the trailer tongue jack. Establish level of the pad with a 4' carpenter's level. Then remove the prop and use a torpedo level to level the prop shaft with the trim buttons , when both are level then pull your straight edge from the bottom of your leveled pad to the center of your leveled prop shaft ,that will be where the prop shaft is in relation to the pad or how high the prop shaft is, both being exactly level and in a straight line that is what is called split shaft ! Or running even with the bottom of the boat's pad or running surface.

Good luck,

Jay @ JSRE

Michael Dixon
07-05-2001, 11:07 PM
Firewalker, I was curious to see if you noticed a drastic heighth difference between the Bob's and the Sportmaster. Although not advisable I could "chop" the throttle with the sportmaster with no bad side affects; but with the bobs even if you ease off the throttle it seems a little awkward. I've dropped it to 1" above the pad and will check it this weekend. Thanks again

07-06-2001, 08:04 AM
Funny you mention that, I have always run extream height with my STV's, as such it has likely caused them to plane on the gear case. I really found that the Bob's made the boat stay up a little longer and also made the back of the boat feel a little wishy washy. My dealer (who is one of the best STV drivers in the world) put his Rocket 200' into the bull rushes while experimenting with a Bob's (this could have also been a function of the Sea Star steering)but he to stated he did not like the feel and the tremendous amount of stern lift it seamed to creat. His had the extended hub. I really feel that the sportmaster is the best behaved case in all respects (except for the XR)


07-06-2001, 10:14 AM
Firewalker, please comment on what you meant by it could have been the Sea Star Steering. What type of steering do you typically run on your STV's? Hydraulic or Manual? Type?

07-06-2001, 10:28 AM
I run Morse, no feed back. We have actually removed the sea star pro from our boats. We were all having problems slowing the boats down and them getting a little darty, we have no problems with the nfb steering.
The steering is a non-issue at speeds below 115