'84 mercruiser 140 stutters while cruising on plane

[swiftsam]

Of course, I finally fix my charging problems with a new alternator, get one great weekend out of her, and now we've got a new problem.

The engine is an '84 140hp 3L.

It starts great and runs fine at idle speeds. It also accelerates and gets up onto plane just fine. Then, intermittently the engine will stutter/stumble/hesitate/almost-cut-out. If I bring it back down to idle it runs fine.

I've seen similar threads that talked about bad gas and low gas that sloshes around in rough water, but I know my tank is full with fresh gas.

It seems like something in the carb plugged up or some sort of fuel delivery problem to me. Anyone have any guesses or good tests to narrow things down?

thanks!

 

[Beefer]

Re: '84 mercruiser 140 stutters while cruising on plane

There have been a number of us with similar problems. I'm still having my issue, but I think I've got it narrowed down to sludge in the fuel tank. Some have reported success with the following, and at least, I'd check them; a new coil, changing all fuel filters, checking fuel pump, timing, dwell, water in fuel system (even with fresh fuel, residual from previously), gunk in tank, and tune-up. There seem to have been quite a few carbs that have been rebuilt, but the problem still existed, so I'm not convinced of a carb issue (on mine) at this point. Those ought to get you started, without costing a fortune.