I have a 1998 310 Sundancer with...

[Summer_Time]

I have a 1998 310 Sundancer with some type of electrical problem.  I have changed 3 batteries, rebuilt a starter, changed an isolator, reset timing on both engines and the problem still exists.  The problem is when running at idle speed or below 2000 RPM's there are no issues.  When I bring the engines up to 3200 RPM's the engines do not have any power.  The port alternator gauge drops drastically and the starboard engine temperature gauge drops from 170 to 100.  I have had several mechanics look at her with no solutions.  Any one have any suggestions or ideas. Thanks in advance. Gary

[Binky]

Are you carb or MPI? I have 98 330 twin 7.4 MPI. Fuel injectors are the weak link, if your spark plugs & wires are good. Alternator may be affected by rpms. Engine temp may be sucking water in thru manifold. Good luck.

[Summer_Time]

Thanks Binky, The mechanic found that I had 0 compression in the no. 7 cylinder. When they pulled the head I had a bent value. This was caused by a leak in the exhaust system. Therefore also affecting my alternator and electronics. Your diagnosis was pretty close. I have carbonated 5.7 Bluewater Mercurisers.
The mechanic is working on her and I will let you know next week if this solves the problem. Thanks for the help. Gary

[Binky]

Cool, I'm glad for you it was "only" a bent valve. I've had two successive (in 3 years) engine swaps (port & starboard), due to cylinders swallowing water on stalling. I just completed the 2nd one. I'm now dealing with eff'd up injectors. Sometimes wish I had carbs.
Good luck getting back on plane. Texas City, TX, Carl

[JRT]

Mine dropped the valve seat on top of the piston, broke the valve, block and head- had to go Mercruiser reman on whole engine! Hope you get out with a bent valve, but it hit something!

[Summer_Time]

Well, we are operational. Took her out for a 3 hour run yesterday and everything worked well. Final results was to replace head on inward port engine, exhaust manifold, riser and elbow. Thanks for the feed back.

Binky we are housed at Waterford harbor in kemah. Where do you dock?