I have 2 of these Prestolite on order from my Gillingham motor factors Superior quality vehicle components in Rochester, they are marine ones. Prestolite Electric & Leece-Neville Alternators – Industry-Best Output is a 70amp one £100+UK vat 20pc. Will use existing pullies I think.
When I get a part number can advise others. I also have a problem with the D+ volts on one engine as I get no ignition warning light when ign on but stationary. I will check to see if any stator 'exciter' volts are appearing with ign on when next at boat. Parts on 2 week+ back order.
Thanks to all info from the post above mine too.