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Merc 75HP, 1986 output voltage

L

leachy

Contributing Member
Hi All,

I was just wondering what the typical output voltage of these motors should be. Im trying to work out if the motor will charge the battery. The battery has enough to start the motor but my electronic battery charger indicates the battery has a fault. When the motor is running and reading across the battery terminals its only in the high 12 volts, doesn't really appear to change with increased revs. The reading is only around 12.7V, Im thinking an internal short in the battery is preventing it from reaching a higher level. even after it has just come of the batter charger its only around that level as well.

Motor is fitted with a new stator and voltage regulator.

Thanks
Leachy
 
Most outboards, of which I am familiar, use low amperage (6A) unregulated supplies at 16V @ max RPM or 9 or16 amp regulated output at 14.5 max at max RPM in the engines below the V6 and up engines whereby some are capable of 40 Amps at 14.5V max RPM.

Battery voltage during charging is dependent upon the batteries charge level. Discharged, or low charge you will get the charging amperage but not the peak voltage mentioned. The battery needs to be full and the charger ready to cut back on charging amps to get to that voltage.
 
Texasmark said:
Most outboards, of which I am familiar, use low amperage (6A) unregulated supplies at 16V @ max RPM or 9 or16 amp regulated output at 14.5 max at max RPM in the engines below the V6 and up engines whereby some are capable of 40 Amps at 14.5V max RPM.

Battery voltage during charging is dependent upon the batteries charge level. Discharged, or low charge you will get the charging amperage but not the peak voltage mentioned. The battery needs to be full and the charger ready to cut back on charging amps to get to that voltage.
Click to expand...
Thanks, that is what I understand as well and for some reason this battery never seems to get above mid to high 12V even just after the battery charger has turned off to trickle mode.
 
Looks like time to load test your battery. 12v is basically discharged. 12.75 is what I look for after the battery has stabilized 24 hrs. after charging. Walmart automotive does that as does Autozone too for a couple of places.
 
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