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Engine won't spin over 6200 RPM

LaveyCraft1976

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I need some guidance. Tested 4 different props on the Stoker 20 SST this weekend from a 26 pitch chopper to a 30 pitch ET. The engine will not spin over 6200 RPM with any of the props that we tried. When we took the cowling off, we could see oil/gas dripping out of the velocity stacks on the carb's and the bottom tray was saturated with oil/gas. Reeds are brand new and the carb's were rebuilt last week. The engine builder told us not to mess with the 100 jets that he has in the thing. I think they're too fat but what do I know?! Any ideas will be greatly welcomed. (Engine is a 2.5 Merc carb motor)
 

Ragged Edge

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My first thought is, as the carbs have just been rebuilt, that the float levels have been set too high or the needle valve is not seating properly. I have seen this with rebuild kits that did not have the correct seat. The hole was too big allowing too much fuel past the needle valve and basically flooding the engine. Ran okay at idle but would not rev. This was a single carb two cylinder sail boat engine.

If possible match up an old seat with a new one from the rebuild kit.

Have you done a compression check lately?
 

sonicss31

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Sounds like floats are set too high or needles and seats are bad. Take it back to guy who did the work or find another guy that knows what he is doing. Not many old guys left that actually can work on carb motors. Everything is plug in diagnostics now. Good luck.
 

stingray11

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What year and motor, has the Rev limiter been onhooked? Have you done full throttle run and turn the key off and check the plugs. It is common for a 2 stroke with stacks to have some fuel dripping out of them but not a puddle.

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LaveyCraft1976

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My first thought is, as the carbs have just been rebuilt, that the float levels have been set too high or the needle valve is not seating properly. I have seen this with rebuild kits that did not have the correct seat. The hole was too big allowing too much fuel past the needle valve and basically flooding the engine. Ran okay at idle but would not rev. This was a single carb two cylinder sail boat engine.

If possible match up an old seat with a new one from the rebuild kit.

Have you done a compression check lately?
Thank you! Compression is 130 across the board.
 

STV_Keith

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First quick test I'd do is put a 22" on it and see if it will turn up. If it won't turn up with a 22", then it's not going to turn up with the bigger props...but if it does, maybe it's just out of power to push the boat any faster. What gearcase, propshaft height, and what does the boat weigh? 1.87:1 ratio?
 

stoker2001

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what Kieth said,Stokers can be VERY heavy so doesn't surprise me..Carb motors will always have saturated lower cowl pan.You will never turn a 30ET lightning prop with that setup..
 

LaveyCraft1976

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First quick test I'd do is put a 22" on it and see if it will turn up. If it won't turn up with a 22", then it's not going to turn up with the bigger props...but if it does, maybe it's just out of power to push the boat any faster. What gearcase, propshaft height, and what does the boat weigh? 1.87:1 ratio?
Keith,

We're going to try a 22 this weekend. CLE 2 hole 2:1 gears, 1/2" below the bottom, and have not weighed the boat. No interior with a center steering setup
 

stoker2001

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Keith,

We're going to try a 22 this weekend. CLE 2 hole 2:1 gears, 1/2" below the bottom, and have not weighed the boat. No interior with a center steering setup
the 2:1 ratio will help to turn the 30ET..No interior helps ALOT also!what carb 2.5 HP rating do you have?the carb racing 2.5s were rated at 245HP
 

Hydroman55

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Never going to spin a “30” with your set up and would say 6200 with a “26” is close.
 

Ragged Edge

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Keith,

We're going to try a 22 this weekend. CLE 2 hole 2:1 gears, 1/2" below the bottom, and have not weighed the boat. No interior with a center steering setup
My experience with the 2.4 carb motor that was on my Stoker when I bought it was that there would be some fuel/oil under the carbs but it certainly did not saturate the entire pan. I cleaned it up after every time out so it never got to spread but it wasn't a big mess to begin with. I still think it's worth checking into. With good compression you can at least rule out bad/broken rings causing blow back.

Also the CLE gearcase is not the best setup for the Stoker. A Sportsmaster works much better, like a couple of miles an hour better.
 

STV_Keith

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Keith,

We're going to try a 22 this weekend. CLE 2 hole 2:1 gears, 1/2" below the bottom, and have not weighed the boat. No interior with a center steering setup
2:1 should make it easier to spin it up. 1/2" below the bottom - any reason for that? Is this an Enduro boat? If not, jack that thing up. 3/4" above the bottom is where I would start. If there is setback (jackplate, etc), go up another 1/4" for every 2" of setback.
 

LaveyCraft1976

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what Kieth said,Stokers can be VERY heavy so doesn't surprise me..Carb motors will always have saturated lower cowl pan.You will never turn a 30ET lightning prop with that setup..
My experience with the 2.4 carb motor that was on my Stoker when I bought it was that there would be some fuel/oil under the carbs but it certainly did not saturate the entire pan. I cleaned it up after every time out so it never got to spread but it wasn't a big mess to begin with. I still think it's worth checking into. With good compression you can at least rule out bad/broken rings causing blow back.

Also the CLE gearcase is not the best setup for the Stoker. A Sportsmaster works much better, like a couple of miles an hour better.
Thank you for the info. We tested the stator and it wasn't getting full advance timing wise due to another wire being zip-tied too tight to the stator wire LOL We're going to go run it this weekend and I'll report back.
 

LaveyCraft1976

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2:1 should make it easier to spin it up. 1/2" below the bottom - any reason for that? Is this an Enduro boat? If not, jack that thing up. 3/4" above the bottom is where I would start. If there is setback (jackplate, etc), go up another 1/4" for every 2" of setback.
Keith,

We do run it in the enduro so that's why we're 1/2" below. We tested the stator and it wasn't getting full advance timing wise due to another wire being zip-tied too tight to the stator wire LOL We're going to go run it this weekend and I'll report back.
 

LaveyCraft1976

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the 2:1 ratio will help to turn the 30ET..No interior helps ALOT also!what carb 2.5 HP rating do you have?the carb racing 2.5s were rated at 245HP
We have the carb racing 245. It's been massaged a little bit by Gibbs. We tested the stator and it wasn't getting full advance timing wise due to another wire being zip-tied too tight to the stator wire LOL We're going to go run it this weekend and I'll report back.
 

Hydroman55

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Speaking of stators I have a spare used one and a 27 pitch prop for just listed in parts thread.

Sorry not trying to steal the thread....Prop may work in this application.
 

LaveyCraft1976

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Speaking of stators I have a spare used one and a 27 pitch prop for just listed in parts thread.

Sorry not trying to steal the thread....Prop may work in this application.
Stator is still good, thank you. What 27 prop do you have?
 

stingray11

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Stator does not advance timing,trigger does that. And yes I have seen far too many trigger wires tied too tight and not allowing them to move and advance timing.

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LaveyCraft1976

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Stator does not advance timing,trigger does that. And yes I have seen far too many trigger wires tied too tight and not allowing them to move and advance timing.

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That's exactly what it was. We are going to replace the trigger in it also.
 

LaveyCraft1976

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haven't ran carbs since 1995,but guessing 100 size jet is WAY to rich?but best to hit the tune rich then lean!!take some jet out and see if it gains RPMs while monitoring piston color..also make sure fuel pressure is stable,guessing 4-5lbs under full load
I feel like the 100 jet is way too rich also, but it's not my engine and it's not up to me, unfortunately. We set the fuel pressure at 4 lbs under full load.
 

STV_Keith

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Keith,
We do run it in the enduro so that's why we're 1/2" below. We tested the stator and it wasn't getting full advance timing wise due to another wire being zip-tied too tight to the stator wire LOL We're going to go run it this weekend and I'll report back.
Well, back when I drove the #234 Stoker, we ran a Mazco 27 at 1" below and would spin it to about 6500. At 1/2" below, maybe you'd get a little more, but I'm guessing anything bigger than a 28 would be too big. What RPM is the motor ported to run at?
 

LaveyCraft1976

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Well, back when I drove the #234 Stoker, we ran a Mazco 27 at 1" below and would spin it to about 6500. At 1/2" below, maybe you'd get a little more, but I'm guessing anything bigger than a 28 would be too big. What RPM is the motor ported to run at?
I'm not sure what it's ported at. I do know my buddy spun it 7500 on his STV Pro Comp 1-1/2" above the bottom.
 

STV_Keith

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Do you know what prop and gearcase ratio your buddy was running? How much setback? What does your boat weight and what did his weigh?
 

LaveyCraft1976

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Do you know what prop and gearcase ratio your buddy was running? How much setback? What does your boat weight and what did his weigh?
He spun a 14.5 X 30" cleaver with a 2:1 coned case. I'd say setback is about 8-10" because it's on a 15" mid with a 20" transom. Not sure of either boats weight.
 

STV_Keith

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So that would be like turning a 14.5x28 with a 1.87 case. 8-10" setback at 1-1/2" up is like 1/2" up at the transom. Turning a 28 to 7500 should be about 98mph. Since I also have a Pro Comp Ski with a similar setup, I'd say that motor should be right about 240hp or so. That's almost exactly what my boat ran with the original 2.4 BP EFI.

That said, you probably want to turn it in the low 7k range. Doesn't sound like it's been ported too much. With your setup of 1/2" below, I'd guess a 27 would be pretty close, maybe a 28 with that 2:1 gearcase...but like the others said, that is really fat. I want to say we ran jets in the mid to high 70's in the 2.0 motors we raced.
 

HST4ME

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I think you have 6100RPM electronic modules and / or maybe the detonation system is kicking in.

Are you getting the warnings from the Ecm (horn beeping/overrev light?)

Do you have a shop manual or parts indenture list for that motor/serial #?
There is this one online but who knows where it came from. here's a screenshot of the page describing the ECMs and detonation control that are around the range you describe.

I really think you are having an ignition limiter incident, - get the part numbers off of the modules that are installed and look into their specific characteristics - but f you are going to start messing with jetting, I have some that may fit: 1399-5225(.054), 1399-4216 (.064), 1395-7831 (.058), 1395-6487 (.060), 1395-6029 (.068), and 1395-6030 (.070)

View attachment 983471
Thats old 3 liter garbage..try again.
 

Christopher Lucero

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Thats old 3 liter garbage..try again.
thats all I've got. It might be difficult to diagnose since this is a built motor that the builder said not to mess with, but I still think checking into to rev limiting settings in the black boxes/ignition modules is worthwhile...pretty easy to do
 

Christopher Lucero

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The 245 wasn't rev limited. I have carb 2.5s ported beyond drag specs that won't pull 100 jets on wmh carbs.
respectfully. you sound authoritative...do you have the manual page or something to make it substantial? I have a selection of jets that may fit if he needs them.
 

rivermobster

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So that would be like turning a 14.5x28 with a 1.87 case. 8-10" setback at 1-1/2" up is like 1/2" up at the transom. Turning a 28 to 7500 should be about 98mph. Since I also have a Pro Comp Ski with a similar setup, I'd say that motor should be right about 240hp or so. That's almost exactly what my boat ran with the original 2.4 BP EFI.

That said, you probably want to turn it in the low 7k range. Doesn't sound like it's been ported too much. With your setup of 1/2" below, I'd guess a 27 would be pretty close, maybe a 28 with that 2:1 gearcase...but like the others said, that is really fat. I want to say we ran jets in the mid to high 70's in the 2.0 motors we raced.
This guy knows a bit about outboards is case anyone didn't know better.

😉
 

LaveyCraft1976

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So that would be like turning a 14.5x28 with a 1.87 case. 8-10" setback at 1-1/2" up is like 1/2" up at the transom. Turning a 28 to 7500 should be about 98mph. Since I also have a Pro Comp Ski with a similar setup, I'd say that motor should be right about 240hp or so. That's almost exactly what my boat ran with the original 2.4 BP EFI.

That said, you probably want to turn it in the low 7k range. Doesn't sound like it's been ported too much. With your setup of 1/2" below, I'd guess a 27 would be pretty close, maybe a 28 with that 2:1 gearcase...but like the others said, that is really fat. I want to say we ran jets in the mid to high 70's in the 2.0 motors we raced.
Thank you for all the info, Keith, I appreciate it. Let's get the STV's together in Havasu when you get yours back together.
 

LaveyCraft1976

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The 245 wasn't rev limited. I have carb 2.5s ported beyond drag specs that won't pull 100 jets on wmv carbs.
I'm still working on the engine owner and builder to try some smaller jets in the thing. I appreciate your input. Where are you located? I would love to pick your brain some more.
 
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Baker343

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Don't know if you got it sorted out. If not I'll give you some thoughts.
Have you tested your carbs to see if 1 or several are puking out of the emulsion tubes.
5 pedal or 7, crossed drilled intake or not.
Wh or Wmv's Carbs.
Have you verified all cylinders are firing. Check all your coils for cracks and good grounds.
Sorry, is this a new mota or just rebuilt carbs.
I'm assuming your setup is correct and your hull is carrying itself and your just down on power.

HST4ME is the Outboard Sensei
 

LaveyCraft1976

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Don't know if you got it sorted out. If not I'll give you some thoughts.
Have you tested your carbs to see if 1 or several are puking out of the emulsion tubes.
5 pedal or 7, crossed drilled intake or not.
Wh or Wmv's Carbs.
Have you verified all cylinders are firing. Check all your coils for cracks and good grounds.
Sorry, is this a new mota or just rebuilt carbs.
I'm assuming your setup is correct and your hull is carrying itself and your just down on power.

HST4ME is the Outboard Sensei
Yes, we tried all of that. Crank trigger was bad so we just replaced it. Gonna see how she does this weekend.
 

Baker343

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If your running WHM carbs some say 68's with 72's as break in. I only know WH's. I'm with Keith 72 to 76 and check your plugs to jet to what each cylinder might need.
Especially the crappy fuel we have and if your building a Enduro motor, WOT for 4 hours. I've learned it's better to be a little fat. Lean doesn't forgive.

And I'm assuming your not running a cross drill intake.
 

LaveyCraft1976

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If your running WHM carbs some say 68's with 72's as break in. I only know WH's. I'm with Keith 72 to 76 and check your plugs to jet to what each cylinder might need.
Especially the crappy fuel we have and if your building a Enduro motor, WOT for 4 hours. I've learned it's better to be a little fat. Lean doesn't forgive.

And I'm assuming your not running a cross drill intake.
We are running WH's also. Pretty sure it's not a cross drilled intake.
 

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HST4ME

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Start with 88"s throw the velocity stacks in the trash and put an air box back on it. What did it start out as...what was it ported to and what series of wh's.
 

LaveyCraft1976

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Start with 88"s throw the velocity stacks in the trash and put an air box back on it. What did it start out as...what was it ported to and what series of wh's.
Thank you. I will get you some more info on the engine.
 
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