Trouble shooting alternator

[Monterey10]

96 Mercruiser 5.7 with the old V belts and what looks like a motorola alternator down there. Last trip out, the volt meter on the dash showed lower and lower voltage. I noticed the electric choke wasn't working. So, I figured the alternator wasn't working. I worked on the choke wiring and the power resumed to the choke. The batteries showed 13 volts with the engine running, then, they settled at 12.6 idle and 12.3volts revving. It looks like I had charge, then not.

So, I wish to know how to verify the alternator is working. In that my problem is intermittent, I'm figuring that the wiring connectors are dirty. (the boat has been sitting) Where could I find the (suspect) alternator wiring connectors?

I could spend a few days pulling the alternator out of the hole, but thought I should check the simple things first.

Thanks in advance.

 

[dubs283]

Re: Trouble shooting alternator

with the engine running in neutral at about 1500 rpm, use a volt meter to check the output at the positive stud/wire on the alternator - should be 14-14.5 volts

check at the starter positive connection, and the battery - should see less than a volt drop across all three connections

 

[Don S]

Re: Trouble shooting alternator

Here is a service bulletin on testing the alternator before replacing.

View attachment Testing Alternators SB 01-12.pdf

 

[Monterey10]

Re: Trouble shooting alternator

Thanks. I get to work with my meter.