Not Able to Go Above 3000 RPMs

[KingstonBayliner88]

G'day,

I'm new in the boating world. I have a 1988 24' Bayliner with a 5.0 litre OMC Cobra Stern Drive. The boat will not climb over 3000 rpms, it runs fine up to and then suddenly bogs down. The previous owner had a similar issue last year prior to finding an issue with the ignition coil that fixed the problem. The previous owner also had new plugs, wires and distributor installed prior to changing the coil that solved the problem. So I've cleaned the carburator, changed up the water/fuel separator (it did have some water) and cleaned the backfire flame arrestor. We checked one of the plugs and it was black. I went out on the sailpast ceremony yesterday and still having issues with climbing above 3000 rpms.

Currently, I have suggestions from my powerboat mates at the club to change the plugs, coil, clean the carburator and jets.

The same propeller has been used for a few years now.

Any suggestions?

Tks.

Jeff...

 

[gdombroski]

Re: Not Able to Go Above 3000 RPMs

If it's a 4bbl that's about when the secondaries open and needs more fuel. I ahd same problem and a new anti-siphon valve ($15) fixed it.

 

[Don S]

Re: Not Able to Go Above 3000 RPMs

Here's a list of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order.

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.