My problem is solved although I have a question, I thought my experience could be some help to someone. My boat is in Mexico where there are no VP mechanics. My alternator began making screeching sounds then stopped putting out voltage. We thought that the alternator was bad after 1000 hours. so we pulled it and tried to find a repair shop but after paying for removal, disassembly and cleaning I was told no parts were available. So I bought two new alternators and pulleys and had a new one installed. I figured if one engine had a problem it would only be some time until the other one went bad. Turns out the new pulley was not exactly the width of the old and instead of the retaining ring holding it on we had to spot weld the end to the shaft it was on. Well the new alternator only put out when I ran up to 2500 rpm. So we figured we had a bad unit and exchanged it for the other one but the same problem occurred. That's when the mechanic tested the wire from the external resistor to two terminals on the alternator and found that the wire was bad and changed it and it worked. I have changed out alternators on boats and cars and never encountered an external resistor on an alternator. I don't know why they would build them that way, it apparently only allows voltage to flow in one direction.
The little wire and resistor costs $90 from Volvo Penta. We just replaced the wire to the resistor but I know resistors cost pennies and wondered if anyone knows the resistor that is needed and I will make a spare.