2004 Merc 4.3L Loss of RPM Problem

[KDN98]

I have twin 2004 4.3 L MPI v6's with alpha 1 outdrives......

I am having a problem with the port engine. It will run fine not under a load.....I can run it up to 4000 RPM no problem. It starts fine and runs great.....Under load if I go over 3000 RPM the engine starts to pop and backs off to a rough idle and then dies. Re-starts no problem. If when I lose power I shift into nuetral and then back to say 2800 RPM it will run just fine....bump it up to over 3000 and same thing. ANY HELP WOULD BE APPRICIATED

Both engines pull from the same fuel take - starboard engine runs great. I have replaced the fuel filter on the port engine and there was no noticable difference.

The boat is a 1982 SeaRay 270 weekender. The engines only have about 30-40 hours on them.

 

[Bt Doctur]

timing not advancing?

 

[chiefalen]

fuel pump giving up the ghost ?. Dirty filter?

Did you do a compression test on that motor ?

So if you find the timing correct cause that is the first thing to look for, i would do the compression test.

Good compression, will tell you also if the valves also need adjustment. Cause bad compression will at least help pin it down a little more.

You can also read the plugs.

 

[KDN98]

Thanks - will try that - what about the map sensor?