Help me diagnose my boat

[KFhunter]

I got a 3L inboard - 1998 vintage with the GM motor. 


The dang thing keeps blowing the ignition or "run" circuit.  I got it narrowed down to the alternator, and what I need to know is if a bad voltage regulator internal to this alternator will cause a heavy load through the charge wire.  On this boat it runs over to the starter main lead then into the battery through the big hot wire.


To muddy things up my battery wasn't fully charged, but it has enough to start the engine ok.   But still I wouldn't think the orange charge wire and alternator housing itself should get so hot.


The orange wire from the alternator is getting really hot from the alternator and up the wire 6 inches, almost enough to melt the insulation.  IT did melt a little spacer insulated bushing that was in there which I removed thinking it was the problem.


So the engine will run a good 15 minutes pulling a big load through the run circuit until finally the 20a fuse is blown out in the fuse panel under the dash. 




boats are so weird to work on

[tony04]

Sounds like you have a short to ground in your alternater. Use a multi meter or ohm meter and put one probe to the wire and the other to the alternator housing.  There should no continuity .

[KFhunter]

hmm thanks


I'm going to pull the alternator and make sure the mounting points aren't corroded.


for the wiring, I don't see anything wrong anywhere, but perhaps it's not pulling a ground through the block?

[buckfvr]

Sounds like you have a short to ground in your alternater. Use a multi meter or ohm meter and put one probe to the wire and the other to the alternator housing.  There should no continuity .

Sounds like a direct ground of the hot wire, could be a diode in the alternator itsself.....have it load tested at O'Reillys......

You can also check for continuity from the ground terminal to the block with the multimeter.