charging problems 898 merc

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dbdupont

Recruit
Joined
Aug 18, 2010
Messages
5
I have a 1983 silverline with a 898 merc i/o. While out fishing I noticed the volt gauge was reading 12 volts with freshly charged batteries, with in a hour the engine started to miss and the batteries were dead. I replaced the alternator with a new mando style 3 wire 55 amp unit. Upon starting the engine ( with fresh batteries) my volt gauge was still reading 12 volts. I am able to start the engine and disconnect the batteries while the motor is running but am not convinced that I have the problem solved. Does anyone have any ideas for me on what to check to fix my charging issues.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: charging problems 898 merc

Well sir -- by disconnecting the batteries with the engine running you may have toasted another alternator. Don't do that! Use a known good voltmeter to check voltage at the battery with the engine running at about 1500 RPM. If the charging system is working it should read in the 13.5 - 14.5 volt range. A battery will typically measure 12.6 volts with the engine off and fully charged. It may be your instrument panel gauge is not accurate.
 
D

dbdupont

Recruit
Joined
Aug 18, 2010
Messages
5
Re: charging problems 898 merc

Will keep my fingers crossed that I didn't ruin the alt. Is it possible that I have an open circuit somewhere and that is putting a load on the alt. If so what would put enough of a drain that would effect the charging system?
 
D

dbdupont

Recruit
Joined
Aug 18, 2010
Messages
5
Re: charging problems 898 merc

Well all charging problems solved. The guy i bought the boat from was a electrical idiot and he sure loved red wire!!!!!! Any way I have the ignition wire and the volt gauge wire backwards. Switched them around and 13.5 volts at the gauge.
 
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