89 3.0 mercruiser, alternater issue?

natsgrampy

Petty Officer 2nd Class
Joined
Aug 31, 2010
Messages
172
Out on the river yesterday for about 4 hours when I got an alarm from the GPS stating "high voltage input". The meter on the dash was pegged to 18 volts, this was at 3700 RPMs. I throttled down to idle and as soon as the RPMs began to drop down the voltage dropped to 14.

I throttled back up without incident for another 20 minutes then the voltage went back up to 18, slowed down again and voltage dropped back to 14. Continued up the river for about another 45 minutes to the dock and had no further issue running at normal speed, say up to 4000 RPM.

Not sure where to start to investigate. Could this be an alternator issue? And what else could create this issue?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: 89 3.0 mercruiser, alternater issue?

Voltage regulator going south!
 

natsgrampy

Petty Officer 2nd Class
Joined
Aug 31, 2010
Messages
172
Re: 89 3.0 mercruiser, alternater issue?

Is the regulator part of the alternator?
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 89 3.0 mercruiser, alternater issue?

Yes, remove the alternator and take it to your local starter/alternator/electric motor shop. They can fix it up like new for a lot less than you can buy a new alternator for.
 

spdracr39

Lieutenant Junior Grade
Joined
Aug 30, 2010
Messages
1,238
Re: 89 3.0 mercruiser, alternater issue?

Also check the water level in the battery. High voltage charging can boil it dry.
 
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