I am trying to update and old 87 supra skiboat. It had a 351 PCM but we replaced with a custom 351. The parts place shipped me the wrong alternator.

The original one had 3 wires.
-orange..positive
-black..ground
-green wire..

The new alternator is like our mercruiser ones with the 2 small gauge wires(pink and purple).

How can I wire the new alternator in? Here is a pic of the wire harness and apic of the new alternator.

black= ground
large red= pos.
purple= excite
pink= ign.

Just to be clear.....

What is the function or where does the "excite" wire go?

What is the function or where does the "ign" wire go?

merc alternarors should be marked.

Merc/mando 4 wire alternators are wired as follows:
Large red, post on alt to starter, supplies the output.
Black, ground, self explanatory.
Purple is the excitation wire. It's on when the key is in run. It tells the alternator to charge.
smal red, or red stripe, is sensor. This meters voltage in the circuit and compensated for loss up to the dash.
You'll need to determine if your pink wire is hot all the time (sensor), or switched (excitation). Then add the needed wire.
What type of connector do you have for the 2 small wires?
Gary

This might help:
http://www.marinemechanic.com/site/page250.html

this may help you too...
http://www.arcomarine.com/xhtml/Tech...tor%20tips.pdf

I think I am pointed in the right direction!

Thanks!