If I send you my Mercruiser 170 engine model & serial numbers, will you tell me what alternator I need or order one for me? I absolutely expect to pay you your profit, overhead and for your time. I'm extremely busy right now and fishing season is starting - I REALLY want to have my boat running for this season.
If the one wire units need higher RPM's to charge, I should probably step up to whatever one works at lower RPM's.
I did some diagnosis using the manual you sent and have a commutator short to ground. I guess the regulator passed the one test I did - I think it was checking for low resistance between the stator wire studs and the alternator case - the resistance was infinite, no reading at all. The epoxy (or whatever it is) regulator filler is cracked and my feeling is to just replace the alternator completely and have a conventional setup. I'll pull the balancer and check for a pinched wire but I doubt that's the problem.