1988 21' reinell 5.7 omc cobra misfiring/voltage issue??

[chad eppig]

Hey all, I am new to this site, I have a problem that has had me stumped for a few seasons on my boat and cant for the life of me figur it out. I have a misfire after its warmed up and put under any load. and at wide open throttle it misses just a bit. the stats on it now are; all new msd marine ignition, msd coil, msd distributor. new manifolds, new risers, just rebuilt the drive as well not that its related. anyways this problem existed even before when it had the oem points set up i would have to run a hot wire to the pos side of the coil to make it run correctly. I have a good idea it is a voltage issue obviously but how and where? Also the alternator is less then 4 years old as well. To add to this my volt gauge on the dash reads about 10.5 to 11 ish most the time and the guages all are wacky all the time for example as i run wot the longer i go the temp gauge eventually pegs itself to 240 and it is not in anyway getting hot i have put an infred temp gauge in all places of the engine to verify. Please help I am losing my mind!! lol thank you

 

[vinnie1234]

Try cleaning your electrical contacts. IF you want to get technical and find out what to clean, you could measure actual voltage at the suspicious contacts against battery voltage. One or two tenths of a volt would not be worrysome, but more than that could indicate corrosion. Clean em up and see if that helps. (goes for gauges as well as ignition system).

You can also measure circuit resistance to ground or pos to see if you have any shorts.

 

[chad eppig]

Hey thanks vinnie! I actually just logged on to see this. I went home last night after work and read the wiring diagram for a couple hours and got my fluke out and traced every power and ground wire until i found the culprit and couldnt believe what i found. The trim gauge that has not worked for at least 7 or 8 years+ was the issue. All the main grounds go into it and from there they branch out the the rest of the cluster and so on.. Anyways the ground coming off it was causing the voltage to drop to 9.1 which fully explains everything. As soon as i relocated the ground every gauge woke back up engine smoothed out and revved up twice as fast like a sb chevy should. Hopefully the lack of voltage didnt already do damage to my msd box or coil.. such a relief.