only reaching 3000 rpms on 3.8 V6 omc inboard outboard.

[steamking123]

I have a omc inboard outboard on a seaswirl 1983. it has a V6 GM motor. When I first got my boat I would reach 4500-4800 rpms with a prop that was 15x17 pitch. at the time it would die at low rpms and back fire occasionally with acceleration. I took it the local shop and had a mechanic go through the carb. he rebuilt it and totally cleaned it. now the boat runs fantastic. idles pefect, no back fires, accelerates good and doesn't die anymore, but it only reaches 3000 rpms. I even put a 15x16 pitch prop on. it still runs about the same 3000 rpms. What would cause a boat to reach 3000 rpm's but also runs perfect in every other way.

I don't know if its relevant but in this process I also replaced the fuel pump. didn't seem like it was related, but still not sure.

I was thinking about replacing spark plugs. any other ideas

Thanks

Derek

 

[Howard Sterndrive]

Re: only reaching 3000 rpms on 3.8 V6 omc inboard outboard.

Only thing to add to this Don S. master list of low rpm issues, is your ESA module (if your boat is 1982-1985). make that #16. You can simply try unplugging the ESA module and try a run
The Don S. list:

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.