Engine RPM hunts while at constant throttle

[prc03sx195]

I hope I can explain this but after the boat has gets on plane while the throttle is at a constant position, the rpm's will not remain constant. It is not a miss just seems like at times the engine doesn't have the power and then catches causing the rpm to change. It just seems like this started happening a few weeks ago, it never use to do this before. I don't know if it is the engine losing power, maybe fuel related or something in the outdrive? Not sure if anyone can help or if I need to post this in a different location, but please let me know. Thanks
BTW, the boat is a 2003 glastron 195SX with a 4.3L I/O mercruiser.
Thanks paul

 

[achris]

Spark plugs.

 

[alldodge]

Is it a carb, and happen to have a serial number?

 

[prc03sx195]

Yes, it is a carb motor. What S/N should I be looking for? I did put new plugs in 2 yrs ago if that helps. Thanks

paul

 

[alldodge]

The S/N will be on the flame arrestor, or on a tag above the starter. Will be a number, one letter and 6 more numbers

I would check fuel pressure while running to see if it varies (3 to 7 psi).

 

[achris]

Yes, it is a carb motor. What S/N should I be looking for? I did put new plugs in 2 yrs ago if that helps. Thanks

paul

Yeah. When those engines start surging, they are saying they want new plugs. I ran a 4.3 GenII for 12 years, and have my current 4.3 Gen+, for about the same time. I have quite a few friends and clients with them too. Whenever I get told the engine is surging in the midrange, I replace the spark plugs and the problem is solved.

Chris...