So -- for the third year in a row, my alternator stopped charging. I'm starting to think this is more than bad luck. It's a minor inconvenience since it is ridiculously easy to change on the boat but I figure there must/may be something else going on. It's ridiculously simple wiring and it all looks like new, any ideas on what to check?

At least two of them were warrantied....

The 1990 Corvettes had a problem with heat and primary
side wiring. The fix was a higher capacity alternator and
bigger primary cable.

I have the same flippen issues! It drives me nuts! It's a one wire alt setup.

POS Alternator company or Charging more than they should or switching most battery selectors while running.

95% of the time it's a POS alternator.

Oh, and warranty, smoranty. That means, who the f*k cares about warranty if all they do is replace the bad one with another bad one.

Exactly. Two new batteries and a good Mondo alt this time. I'm tried of messing around.

its probably the voltage regulator failure could be bucking each other on a twin engine setup..for start up i put my switches on all or both. after running i put one switch on 1 and the other on 2

Running down a battery (stereo) then using alternator to charge drained battery will overheat and kill it.

Clean you grounds and make sure theres no paint on any of the mounting surfaces of the alternator. The same thing kills amplifiers too.

Since we're here is their any preferred make of batteries? Or is this the same question as what's the best oil for my boat.

Sears Diehard platinum or odyssey group 31 size since you asked.