motor issues? max rpm not even close

[garmin0204]

ok guys i am new to this i just got my 1989 21ft larson senza up and running but it just doesnt seem to want to break 4200 rpm and i am not sure why here is a quick run down of what it has 5.7l chevy/mercruiser, procomp alum chevy heads 2.02/1.60 valves with 1.6 roller rockers, comp marine cam,complete msd ignition (box,coil,billit dist,) edelbrock performer eps intake manifold, edelbrock 600cfm carb, through hull exhaust, alum exhaust manifolds
se-106 outdrive 3 blade 20pitch prop

just changed outdrive gear oil, changed engine oil and filter (40wt with k&n filter) timing is set to 8* initinal with a total advance of 29*, and installed new fuel/water seperator, and fuel pressure is around 4-5psi.....it revs fast and revs to 6k rpm on land in neutral and in water it gets up on plane fast and gets up to 4200 fast but its like it hits a wall and i also checked to make sure the carb was opening all the way and it has fresh 93octane fuel

 

[Showtime22]

Re: motor issues? max rpm not even close

Try a lower pitched prop. The 20 pitch may be holding it down.

 

[WAVENBYE2]

Re: motor issues? max rpm not even close

Try a lower pitched prop. The 20 pitch may be holding it down.

Try a 19p. should raise your RPMS

 

[cr2k]

Re: motor issues? max rpm not even close

What is the gear ratio of the outdrive? If you got a big block ratio it will be too high to spin up. In this case you would need a lower pitch prop.

I haven't heard much either way on these outdrives.

 

[garmin0204]

Re: motor issues? max rpm not even close

not sure of the gear ratio and i cant find any serial #'s on the drive it just says se-106 on it...any suggestions how i could find out gear ratio?

 

[ziggy]

Re: motor issues? max rpm not even close

this was written up a long time ago by someone else. i just saved it. don't know who wrote it. but i'd imagine this would fill the bill...

Do all these steps in order.
1. Shut off the battery switch
2. Pull the spark plugs out of the engine.
3. Put the shifter in forward.
4. Turn the engine till the prop starts turning, continue turning till the timing mark is at TDC.
5. Put a mark on the prop hub and the drive housing that align with each other.
6. Turn the engine by hand while someone watches the marks on the prop, and count the revolutions the crankshaft makes to turn the prop 1 complete revolution.
7. If it took 1.5 revolutions of the crankshaft, then you have a drive ratio of 1.5:1 which is what is needed for a small block V8. (a 260).

hum, bubba beat me to it. pretty speedy bubba....

 

[garmin0204]

Re: motor issues? max rpm not even close

no it hasnt been on a scale..ill check the ratio when i get home ...and ill post results

thanks

 

[garmin0204]

Re: motor issues? max rpm not even close

how many rpm's should i gain with each degree in drop of my pitch i have read 200-300 each degree is that correct because if my outdrive is the correct ratio i would have too drop alot in pitch to bring up my rpms right?

just got home from work tonight no time to check ratio tonight but will tomorrow any other idea's for things to check?

 

[TilliamWe]

Re: motor issues? max rpm not even close

garmin, you would think that you would need to drop a lot of pitch to make the rpms go way up, and normally you would. But I'll guess that you have that motor set up to make it's horsepower at 5000rpms. So right now, you can't get there with your current prop. But a drop to a 19p, which should only raise the rpms by 100 to 200, might let the motor get into it's torque and hp curve, and voila, it might rev to the 5000 mark. See what I mean?

 

[garmin0204]

Re: motor issues? max rpm not even close

i see so that might be just enough to push it over the edge and let it rev.. should i get the 19 or an 18 pitch prop?

 

[Honest Don]

Re: motor issues? max rpm not even close

Anybody wanna look at the obvious here? a 600 cfm on a hot rodded 350??? way too little carb. should be atleast a 670 if not 700. stick with vacuum secondary's and your throttle response will remain the same. Also the 8 degree initial timing is low. depending on the cam it would probably like a little more, with a total of 30-35 all in by 3k, but call the comp tech line and find out what it needs.

Because it's doesn't cost anything, I'd put a little more timing in it and see what happens. If it revs without a load, it would seem to me to be a fuel issue though. You can go to the holley website and they have a tool to pick the right carb. Check it out, and I'm sure you'll be surprised.

 

[45Auto]

Re: motor issues? max rpm not even close

I just went through the Holley carb selector for Garmin0204's engine and it recommended the 600 CFM Model 4160 ......

 

[Bifflefan]

Re: motor issues? max rpm not even close

5.7l chevy/mercruiser, procomp alum chevy heads 2.02/1.60 valves with 1.6 roller rockers, comp marine cam,complete msd ignition (box,coil,billit dist,) edelbrock performer eps intake manifold, edelbrock 600cfm carb,
timing is set to 8* initinal with a total advance of 29

Why the 1.6 rockers? 1.5 is all you need and if you have a big cam then 29* timing is not even close. Also if you have the big cam the 600 cfm isnt doing you any favors eather. Your looking for the widest torque curve you can get.
What do you have for cam specs?

 

[Honest Don]

Re: motor issues? max rpm not even close

I had the same issue with the new 355 in my 19' cuddy. Had a holley red pump, edelbrock rpm intake, petronix dissy and coil, and a 650 vac sec spreadbore holley.

I began playing with jets to tune it, but without an engine dyno it's extremely time consuming. When the end of the season came i gave up and started my search for an EFI set up. Ended up scoring a deal on a holley stealth ram, and now the thing is a screamer. The throttle body is a 58mm and rated at 1000 cfm. Not a good idea for a carb because of jetting issues, but the injectors are also dumping the right amount of fuel.

If fuel pressure is good, and your happy with the carb choice, try to fatten up the mix by re-jetting. a 21' boat with a stout 350 and a 19/20 pitch prop should run mid 50s. depending on weight. I have a friend of mine with a 21 closed bow and oem omc 350 that runs mid 50s with a 19 pitch aluminum... nothing special.

Another thing to look at is cam timing. If it was installed advanced too promote low end, but done without a degree wheel, or "close enough" it will hurt your top end. Advancing or retarding your cam timing only moves the powerband it doesn't change it.

I still say look at fuel/air delivery, and bump up the timing.

 

[TilliamWe]

Re: motor issues? max rpm not even close

Anybody wanna look at the obvious here? a 600 cfm on a hot rodded 350??? way too little carb. should be atleast a 670 if not 700.

I disagree. Small Block Chevies do not need a lot of carburetion. Even hot rodded ones. A properly functioning 600cfm carb will work just fine. A 650 would be the Max he needs in a boat.
Garmin, is the carb functioning properly? And you understood exactly what I was trying to explain about the smaller prop getting the it "over the edge". Now if the secondaries on the carb aren't opening properly, all the little props in the world aren't going to help.
Nothing weird going on here, like the engine compartment is sealed so well that the engine is starving for air, is it garmin?

 

[garmin0204]

Re: motor issues? max rpm not even close

ok the carb is brand new and has mech. secondarys and here are my cam specs also..i have a 750 should i try it ? but its a car carb really no diff. right?

Brand COMP Cams
Manufacturer's Part Number CL12-232-3
Part Type Camshaft and Lifter Kits
Product Line COMP Cams Xtreme Marine Cam and Lifter Kits
Summit Racing Part Number CCA-CL12-232-3
Cam Style Hydraulic flat tappet
Basic Operating RPM Range 1,000-5,000
Intake Duration at 050 inch Lift 212
Exhaust Duration at 050 inch Lift 218
Duration at 050 inch Lift 212 int./218 exh.
Advertised Intake Duration 256
Advertised Exhaust Duration 262
Advertised Duration 256 int./262 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.447 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.462 in.
Valve Lift with Factory Rocker Arm Ratio 0.447 int./0.462 exh. lift
Lobe Separation (degrees) 112

my lift is alittle diff because of the 1.6rr it is
intake is 0.476
exhaust is 0.492

 

[Bondo]

Re: motor issues? max rpm not even close

i have a 750 should i try it ? but its a car carb really no diff. right?

Nope,... Don't even Think about it,... Automotive carbs equal a Bomb on a boat motor..

A 600/ 650cfm carb is Plenty,....
A 350 screaming at 5 Grand can only move slightly LESS than 550cfm....
A Bigger carb screws up the vacuum signals,+ creates a Dog of a motor...

 

[WizeOne]

Re: motor issues? max rpm not even close

ok the carb is brand new and has mech.

Yes but not entirely. The secondary butterflies are opened mechanically but there are vacumm operated 'air doors' at the top of the secondary venturiis. You want to make sure those are opening.

You should also pull the plugs and take a reading after a high speed run attempt. If you are not delivering enough fuel, the plugs should show it.

 

[QC]

Re: motor issues? max rpm not even close

Before you do anything else we need the drive ratio (call SEI they may have a record of it) and it would be nice to have your Garmin speed numbers. Even though this may be a higher revving engine, decent speed at 4200 would tell us that it's making power and that pitch may be the only issue.

it revs fast and revs to 6k rpm on land in neutral

No load revving is meaningless and potentially damaging.

If it revs without a load, it would seem to me to be a fuel issue though.

Well maybe that indicates the ignition is igniting, but it still seems to me we are trying to:

a) blow these things up on the trailer and

b) fix something that has not been confirmed is broked . . .

 

[garmin0204]

Re: motor issues? max rpm not even close

ok i just checked my outdrive ratio it is 1.5 crankshaft revs to 1 turn of the prop.. had it out saturday and was next to my buddys center console he was running at 40mph WOT and i pulled away from him pretty fast it seems to be running in the 50's but only 4k rpm so maybe its just prop pitch i hope another thing i noticed was on my mech. fuel pump there is a line on the top which is capped off if uncapped it and it seems like there is air comming out of it whwile the boat is running but not sure i am going to put a psi/vac gauge on it to see what its doing , does this get hooked up to anything the guy i bought the pump from said it was always capped on his boat.. also i added some timing bringing it all in by 3krpm i had it to 35 total and no difference in performance..
prop is : michigan wheel 033078 rapture series standard rotation
dia. is 14.25" .. 3 blade
pitch is 21 i thought it was 20 thats my fault

thanks for all the help