MERC V135 Alternator help

[Fin-ster]

Hey guys,
This one should be a piece of cake for you guys so here goes. My 89 V135 doesn't seem to be charging back to the battery. I gave the battery a fresh charge to start the season and went out three times. on my last trip I finished a drift while fishing and went to reset and no power. So I threw the anchor and waited for TowboatUS to come. by the way great service from those guys I highly recommend it. Anyway, how do I check to see if its the alternator. and how hard is it to replace it?
Thanks,
Shane

 

[WillyBWright]

Re: MERC V135 Alternator help

The alternator consists of magnets in the flywheel, the stator under the flywheel, and probably two rectifier/regualtors. Of those, the regulator/rectifiers are the most likely to fail, although stators can too. Yours probably has two regulator/rectifiers sandwiched between the exhast cover and coil plate. Originals have pale green clear potting and you can actually see if they have failed. They leave obvious brown discoloration in the potting. The most common causes of regulator/rectifier failures are crossed, corroded, or loose battery connections. If connection between the battery and outboard is momentarily lost, electricity already produced in the stator will find it's way someplace come hell or high water. Usually by arcing inside the regulator/rectifier. The heat from that arcing is what discolors the potting. It's very common. I see it several times each year.

To see if your system is charging, put a voltemter on the battery. If voltage rises with RPMs, it's charging. It should climb as far as 14.7v at full RPMs if you're running the boat in the water. On a hose with muffs, it should rise above 13v at high idle.

 

[Fin-ster]

Re: MERC V135 Alternator help

I'll definitely give that a shot. Thanks a ton for the advice. I haven't had time to care care of it with school and all but I will be working on it on friday.