alternator charging issue

[87 AJ 270]

Does anyone know what alternator came on a 1987 V6 175 Mercruiser? Alternator make and amp output? I've got twin v6's charging 3 batteries, 1 engine charging 1 battery and the other engine charging 2 batteries. The 2 battery bank is getting a high charging rate. i'm wanting to add a battery isolator to help save the alternator from trying to charge both batteries at the same time. I've got a Sure Power isolator but I have to know what alternator I have to make sure they will work together.
Any other ideas would be appreciated.

 

[JimG]

Not sure of your intentions... isolators are typically used to keep one battery from discharging into another.

 

[Fun Times]

Chances are it's going to be a 55 amp, Below is a link to your engine parts for your engine, Two of the three alternators in the link below say 55 amp, To know the other one you will need mercruiser serivce manual #7, Merc part number 90-12410 that covers your engine, The information should be in that service manual.:smt001 Good luck with it.:smt001

http://www.mercruiserparts.com/selectDocs.asp?doc_nbr=17468

 

[87 AJ 270]

Thank you for the info, I really appreciate any and all suggestions and info.:smt001
I do know the isolator is rated for up to 120 amps and I'm assuming the alternator is post 1985 GM since it is a 1987 SeaRay. The isolator has several wiring options for pre & post 1985 alternators. I ran the ole' girl around the inlet and checked the output gauge on both alternators, the one alternator with the single battery was pushing 13-14 volts, and the alternator with the 2 battery bank was pushing up to 16 volt. I'm going to add another gauge and split the 2 batteries just to see what each one is getting. Any better ideas?:huh:
Thanks

 

[Kay Lee]

If your output voltage is too high, then most likely the regulator in that alternator has gone bad. Verify the actual voltage using a VOM or DMM set to at least 15 volts DC and measure right at the battery posts with the engine running.

Larry

 

[flarepoman]

Here is a good place to get alt's http://www.arcomarine.com/
I have 1 starter from them and 1 alt.

Fair prices and fast service, Rick