Bad alternator 228 mercruiser 79'

[Minz06]

So need a little help... It seems oem alternator put out 37 amps. (QUICKSILVER ALTERNATOR 78403A2 at MarinePowerService.com) I went to autozone and they had something on the shelf a little different than mine but made for mercruiser boats.....(12176N-1G - WPS) It's 65 amps so long question short.... Am I ok with this 65amp instead of my oem that's 37amps. I've already installed the 65amp and ran it in the driveway seems fine but volt gauge was reading roughly 15volts..... Thoughts?

Oem part number-78403A2
What I bought-12176N-1G

 

[Bt Doctur]

Re: Bad alternator 228 mercruiser 79'

Iboats has a better deal
http://www.iboats.com/Mercruiser-Al...7428548--session_id.368896887--view_id.269735

 

[Bondo]

Re: Bad alternator 228 mercruiser 79'

So need a little help... It seems oem alternator put out 37 amps. (QUICKSILVER ALTERNATOR 78403A2 at MarinePowerService.com) I went to autozone and they had something on the shelf a little different than mine but made for mercruiser boats.....(12176N-1G - WPS) It's 65 amps so long question short.... Am I ok with this 65amp instead of my oem that's 37amps. I've already installed the 65amp and ran it in the driveway seems fine but volt gauge was reading roughly 15volts..... Thoughts?

Oem part number-78403A2
What I bought-12176N-1G

Ayuh,.... A Bigger alternator will only make the required power that's asked of it,...

Whether it's a 37 amp, or 137 amp, it'll still only charge the battery to full, 'n stop,...

 

[Minz06]

Re: Bad alternator 228 mercruiser 79'

My main concern is that the volt meter on the dash is reading just a hair over 15 volts... I thought the highest it should be is like 14.something.....

 

[Augie56]

Re: Bad alternator 228 mercruiser 79'

I wouldn't be too concerned with that, the charging voltage coming off a new alternator may be just a hair higher than the 14.5-14.8 V that is the usual voltage. It won't damage anything.

And like Bond-O said, the extra amp capacity of your new one will only be "used" if you connected something that would put an extra load on your electrical system (like a big sound system, 120VAC inverter, etc). Oherwise, the batteries and boat will draw what they need and that will be it.

 

[Minz06]

Re: Bad alternator 228 mercruiser 79'

So now I'm having troubles again. At first I thought I needed a new deep cell battery....I bought one installed worked fine for about 2 trips then starting power was weak again. Bought new alternator, a good one worked fine for about 2 more trips. Now I was out yesterday and same problem hardly starting.... My question is, I never tested the other old battery would that cause the other to drain? And also.... When the boat is running it reads on the dash 14 volts now so that would mean that the alternator is working and wired correctly right?

 

[Bt Doctur]

Re: Bad alternator 228 mercruiser 79'

Some basic testing first.battery cables, cable ends, cable connections(both ends) ,clean, no corrosion, no bulges in the cable themselves
Multimeter at alt output post ,reading???, meter at battery post, reading at 2000rpm ,?????

 

[Minz06]

Re: Bad alternator 228 mercruiser 79'

That's next is finding my multi meter and checking output of alternato. I just wasnt sure of that one old battery could cause this much of a poblem even with 1 new battery and a new alternator.