my 86 Merc 3.0 wont charge good...altenantors fine??

by John
(Mass)

I have 86 merc cruiser 3.0 ...the altenantor is fine... when positve cable is hook up to battery it barely put out 12 volts... when positive cable is disconnected votage jumps up to14 v like it should???? Jmarshallgray@gmail.com

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Aug 05, 2016
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stumped
by: jeremy

Same problem with 92 glasstron with. 4.3 mercruiser. New battery and alt.it will get good voltage when battery is disconnected. When the battery is hooked up it gets 10.5 volts. Help

Jul 23, 2014
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Check teh battery
by: John

Get a load test done on the battery, if a battery is relatively low it takes some time for a voltage to build up or if sulfated it will never come up. Never disconnect the alternator when charging or you will blow the alternator rectifier diodes. A fully charged battery will be about 12.5 volts