Alternator question

R

Ron-O

Petty Officer 2nd Class
Joined
Jul 30, 2007
Messages
106
Just had the carb rebuilt and reinstalled today. The mechanic looked at my volt gauge and said it should read higher than 12 volts while the boat is running. He checked my alternator and it maxed out 12.5 volts while running. The alternator says Mercury 19685. It's on my 1991 Cheetah with a 4.3 mercruiser. Also what size belt do I need. I'd like to order tomorrow to have everything ready to install this weekend. Sierra sells an alternator with 65 amp not the 55 amp that I have.

Ron
 
chiefalen

chiefalen

Captain
Joined
May 18, 2008
Messages
3,598
Re: Alternator question

You can put the 65 amp no problem. E-bay has them. So long same wires in back. And marine of course.
 
Vic.S

Vic.S

Rear Admiral
Joined
May 4, 2004
Messages
4,701
Re: Alternator question

At 12.5 volts you wont be charging, at least barely. Depending on spec you should be getting up to around 14 volts,

There could be several reasons, apart from a slack belt. Rectifier, brushes or most likely regulator.

Get the alternator off and checked it will easily be repaired and at a fraction of the cost of a new one.

Also get your battery recharged. Leaving it in a partly discharged state will shorten its useful life dramatically.
 
H

hard-3

Petty Officer 2nd Class
Joined
May 29, 2006
Messages
154
Re: Alternator question

the voltage regulator should go up to 14.2 volts sometimes the diodes blow and take out the voltage reg. take it off and go to a good rebuild shop that specialize in auto electric systems they can test and rebuild what it needs charge battery good and load test it
 
R

Ron-O

Petty Officer 2nd Class
Joined
Jul 30, 2007
Messages
106
Re: Alternator question

Called around for rebuild costs, the shop I've used before said $120 for a rebuilt one. (Some reason he said it's not worth rebuilding the old alternator?) I can get a new Mando for $165.... And for a new belt, looks like I need a 44" or 46" depending on water pump pulley size...
 
JustJason

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,319
Re: Alternator question

i bet you have wingnuts on your battery right?
 
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