Engine gains rpm's and overheats.

[fdnyff]

I have twin 1996 225hp Salt Water Series II w/ carbs., mounted on my 1989 26' Sea Ox. The starboard engine is gaining rpm's when on plane. I sync them up at 3800-4000 rpm's, but then the starboard engine revs up and down 300-400 rpm's. If run like this long enough the engine overheats. If I lower the rpm's just enough so it doesn't rev, the engine doesn't overheat. I trimmed the engines all the way down and the trim tabs are not the problem. I had the props re-hubbed and even changed to another set of props. I changed the plugs again and the wires look good. I didn't notice any arcing. Any thoughts, maybe a bad coil?

 

[bowhuntrrl]

Re: Engine gains rpm's and overheats.

I don't know about the overheating, possibly time for a thermostat or water pump kit, but the over revving could be a spun prop hub.

 

[fdnyff]

Re: Engine gains rpm's and overheats.

I don't know about the overheating, possibly time for a thermostat or water pump kit, but the over revving could be a spun prop hub.

Thanks for the reply. I re-hubbed and also changed the props. That's not the problem. I still have the revving by about 300-400 rpm's in the 3800-4200 range. I was thinking it could be a bad coil or perhaps water in the carbs. I'll drain the carbs. I'm not sure as to how to check the coils. I changed the water pump again and that seems to have solved the overheat problem.