3.0L OMC GM motor stalls when run high RPM

I have a 3.0l omc inboard, it is in a 1988 capri B/R. The boat sat for the last five years but was winterized before setting. I bought it replaced coil , points and rotor. Added fuel with carb cleaner. Started up and ran pretty smooth in yard with muffs. Let it run to make sure no over heating or block leaks occured. Voltage at coil at 12.8. I put in water ran about 30 mins. Up and down on throttle then out of no where started to skip and back fire. eventually stalling. Would not start. But after about 15 mins. it started up. Headed back to launch slow at first then tryed faster for a short period. The same thing happened agian. Started after it sits awhile. Got back to yard put old coil back on took thermostat out although temp while running stayed between 175 and 190. It idles smooth in yard but skips some what above 3000 rpm but does not shut down. Hope can give me some advice on where to look. Thanks Wayne

Re: 3.0L OMC GM motor stalls when run high RPM

Start with simple (cheap things) that could both cause similar problem. Change fuel filter/water seperator and anti-siphon value. If that doesn't fix move up to ignition issues.

Re: 3.0L OMC GM motor stalls when run high RPM

Sounds as if your fuel tank is not venting...and developing a vaccuum, that restricts your fuel flow. This takes a while to happen...and goes away from sitting between engine runs.

I would try the boat on the water again...but 'crack' the tank filler cap, to avoid a vaccuum.

Re: 3.0L OMC GM motor stalls when run high RPM

Mine did that but I found my point gap was too large