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Weird!

805HD

Regular Contributor
New engine in the boat, (454 mercruiser in a ‘87 cobalt). Having a slight issue. Once the engine warms up I get what im assuming is a misfire (engine studders) between 1500-2000 RPM while at the same time the needle on the voltage gauge bounces around like crazy. Any ideas? Where would you start.

also I’m getting engine feed back through my speakers.

obviously an electrical issue, all my grounds look good, batteries are all good. I sanded all my ground contacts nice and clean with no change.

thanks in advance!
 
Rotor windings in alt may be going bad

interesting point.. that alternator is maybe a year old and is making 14+ bolts while engine is running.

is what’s weird is that the probably only occurs once the engine is warmed up and only between 1500-2000rpm. If I power through it and ask for my throttle the boat runs just fine.

weird
 
It could also be a bad engine ground(s). I'd start the analysis by disconnecting the alternator (since that's easy to do).

If no change, start looking for a bad ground(s)--which is much harder to do. It's entirely possible that, at that specific rpm, the vibration wiggles a bad connection enough to cause the problem, whereas the connection behaves itself other wise.

Good luck!

Jeff
 
It could also be a bad engine ground(s). I'd start the analysis by disconnecting the alternator (since that's easy to do).

If no change, start looking for a bad ground(s)--which is much harder to do. It's entirely possible that, at that specific rpm, the vibration wiggles a bad connection enough to cause the problem, whereas the connection behaves itself other wise.

Good luck!

Jeff

yea I initially assumed it was a bad ground as well, especially because of the engine feed back coming through the speakers. But don’t you find it odd that it won’t do it cold?

boat runs fine for 40 mins or so then starts missing. And it’s directly related to the voltage gauge because that needle bounces like crazy while the miss is happening.
 
Also, I just went out to the boat and disconnected the orange wire coming off the alternator. The speaker feedback I was getting is gone now.

what in the heck is going on?

i checked all my grounds, cleaned all the contacts, everything is tight.. I don’t understand!
 
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