have problems with AQ151

The problem is that the port engine has a very inconstant idling a almost always stops wnhen most needed (manouvering).

Also and most important when at sea the engine doesn't go over 3000 rpm, and
at this point make noises like popcorns on the oven.

At neutral none of this hapens ( noise ) and the rev counter goes up normaly.

Already changed the plugs, and the problem maintains.

The other engine works fine.

Also and most important when at sea the engine doesn't go over 3000 rpm, and
at this point make noises like popcorns on the oven.

Click to expand...

Ayuh,..... Sounds like a fuel delivery issue, it's runnin' Lean,.....

'n Don't let it make the popcorn sound, as that's the motor destroyin' itself,.....
That noise is Detonation,.....

Suggestion:

Look up your OEM ignition advance specifications for your engines.
You will find what we call BASE or Initial Advance, and you will find an advance curve.
With your strobe light attached, look at what your engine is seeing for BASE advance.
If not to specs, make the adjustment!
Now increase RPM as you strobe and look at what the system is offering for a Progressive Advance and for a Total Advance as per engine RPM.
There will be an RPM at which the system gives Full In advance.
From what you see at idle RPM to Full-In RPM is your ignition advance curve.


Both engines should be seeing very close to the same advance curve.

Any gasoline engine that is not given the correct ignition advance, will suffer in power and performance.