engine backfire
 

Had the boat out yesterday and the port engine started to lean pop out the carb under load. 1995 HP 500's carb motors, would be ok at idle and slight load (under 1500 rpm) but unable to bring it up higher. I am thinking my coil is going bad or a bad cap and rotor, has anybody had this happen before ? fuel pressure is good temp and oiil pressure is good, wires are MSD 8.5 reds and coils are the high vibration coils but are a bit older. Runs and starts grerat at idle but once it warms up and under load lean pop out the carb. no black smoke or rough idle at all.

check your accelerator pump.

Cam lobe or valve spring are also possible causes

Well i dont believe it to be carb related as idle and acceloration and light load is ok, it is speratic and not constant. feels more like electrical related.

head gasket leak

possibly timing, coil is also likely.

Probald meg kicserelni.

Good name Laszlo. Szervusz
:cool-smiley-027:

Sounds like a valve or spring problem

Battled the same problem on my Ski Centurian for over a month. Kept thinking it was an electrical problem. Fuel pressure good, float level good, accelerator pump good. Finally replaced coil....No bueno. Finally realized it was happening only under load with the 4 barrels open. I pulled the bowls and sure enough, one tiny air passage was plugged on the secondary side. A bit of chemtool and she runs good as new.
I would have bet big $$$ it was electrical, until I cleaned the carb.



Darrell.

Had a similar issue with mine and it turned out to be a fuel seperator.

I've had the same symptoms and the end result was a bad rev limiter box.