Low RPM's

[wvflyboy]

I have a 1997 270 DA with a 454 7.4 LITER with a Bravo III drive.
It's been running find all summer - but yesterday afternoon when I took it out I could only get it to generate about 2600 RPM's at full throttle.

The engine did not sound that bad and there was no smoke.... but that's all the get up and go I could get out of her.

Any suggestions on what to look at?

Thanks,

Mike

 

[EricW]

Any chance the hull bottom has some growth now?

 

[Quint4]

Most of this will apply to your boat.

Engine Won't Reach Operating RPM (WOT). 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
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
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.

 

[GMAN1]

Pull plugs and do compression test. I would start there and report back.

 

[Dick Whetstone]

If you leave the stern drive in "neutral" (push the disengage button) and advance the throttle briefly to WOT does the engine reach rated RPM quickly without hesitation or missing? I realize this simple test does not put the engine under a load, but if the engine easily reaches rated RPM without issues, I would check the bottom for marine growth (crud).

 

[wvflyboy]

Thanks for all the replies.

When I went out the other night it got up to 3400 RPM's. It seems to be running a little ruff. I was down to my last 4th of a tank of gas and someone suggested that I might have some water or crud in the fuel.

I through a can of gas stabilizer in the fuel system and filled the tank to half way. It now goes up to 3500 RPMs and seems to run a little smoother.

I'll keep you posted - but I appreciate your feedback.