Thanks for the tips everyone. I suspect a wiring issue as (I believe),
I should have voltage on the regulator. I have two battery banks, one
that has 2 6volt golf cart batteries for the house, and one separate
marine starter battery that is just to start the engine, nothing else.
I intentionally ran down the house battery to test the alternator.
When I ran the engine and tested the voltage on the alternator, it read
12.42 volts, which was the same as the house battery before I started
the engine. When I switched the control to charge the starter battery,
I read 12.75 volts (the same as the starter battery before running the
engine). So, the alternator reads what the voltage is on the
batteries, but is not charging them.

I'll follow the steps to bypass the regulator to see if the alternator
is functioning. I hope it's wiring issue, that would be a lot less
expensive to fix! If the alternator is out, I fear I've got a bigger
issue because I had it professionally rebuilt about 6 months ago.
So..that would mean something caused it to burn out.

Thanks again for the tips. I'll keep you all posted.

Peter