4.3L Mercruiser low RPMs

[hertelke5928]

Hi Guys

I have a 1986 205 HP 4.3L with a Alpha One outdrive on a 1986 Sea Ray 210 Seville. The boat didnt't want to run when I first put it in this year. Since then I have had the fuel tank cleaned out, new fuel water seperator, new filter in fuel pump, new distrubtor cap and rotor, new plugas and wires and rebuilt carb. The boat will plane out with one ore two people on it but doesn't seem to get much over 2800 RPMs. If I put 4 people on it she does not want to plane out at all. I was thinking it was a fuel starvation problem but am now lost.

Thanks in advance for any insight

Kevin

 

[Don S]

Re: 4.3L Mercruiser low RPMs

Here is 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.

 

[thedillybar]

Re: 4.3L Mercruiser low RPMs

And everything on the list is worth checking. If your current setup used to run well & doesn't anymore, you can eliminate some like propeller pitch & wrong gear ratio in outdrive...

 

[fsjcowboy]

Re: 4.3L Mercruiser low RPMs

Broken flapper valves can be like shoving a potato in your exhaust pipe.

 

[Yachtsman1304]

Re: 4.3L Mercruiser low RPMs

The first two things I would check would be the fuel pump and the fuel tank vent. Just ask me how I know this!