1996 4.3L V6 Mercruiser - max @ 1200rpm

[MattSm]

Recently purchased a 1996 Bryant with the above motor / out drive.

I’ll get right to it. Starts fine. Idles fine. No backfiring or bogging of any kind.

When on the water she gets up to 1200 rpm’s normally but will not go past that. Stops at 1200 and will not even attempt WOT.

When pushing the throttle to WOT, slowly or quickly, nothing happens. No knocks, backfiring, no abnormal sounds at all. It simply does nothing and sits at 1200rpms

What in the world is happening?

 

[Scott06]

Recently purchased a 1996 Bryant with the above motor / out drive.

I’ll get right to it. Starts fine. Idles fine. No backfiring or bogging of any kind.

When on the water she gets up to 1200 rpm’s normally but will not go past that. Stops at 1200 and will not even attempt WOT.

When pushing the throttle to WOT, slowly or quickly, nothing happens. No knocks, backfiring, no abnormal sounds at all. It simply does nothing and sits at 1200rpms

What in the world is happening?

I guess you didn't do a water test?

Would look at a couple things starting with basics- Do you have serial number so we can see what you have ? - assuming it is a 2 bbl carb with Thunderbolt ignition?

Check compression and firing order on spark plugs, check ignition timing including total advance , what do spark plugs look like, verify choke is fully opening, take off fuel filter dump contents into clear jar- look for debris water or phase separation.

 

[kirkll]

This may sound really basic…. But have you checked your throttle cable out? Maybe disconnect the cable and run the throttle by hand and see what happens…. When I first got my old 1990 boat with the same motor, I had to replace the throttle cable going to the remote. Just a thought.

 

[MattSm]

Thanks for the tips.

I made some progress. Turns out the carb was not opening completely. I remedied that so now…

I get proper rpm’s in throttle only mode however still nothing above 1200rpms when under load.

 

[Scott Danforth]

I get proper rpm’s in throttle only mode

Means nothing. The motor will spin 5000 RPM on 2 cylinders running on bad gas

Motors under load need all their cylinders and lots of fuel

Do a load balance check
Do a compression check (should be 150)
Measure fuel pressure
Check timing
Replace the fuel filter and check the contents of the filter in a clear container