Battery issue Mercruiser 3.0

[trooper1954]

Hi all,
Have a 1989 Searay with a 3.0 liter merccuiser engine. For the last little while when under way the engine stalls...it restarts but always with a slugish battery turnover. I removed the battery and fully charged it to 13.7v. then returned it to the boat. I put a multimeter on the cables that go to the battery from the alternator, and got a reading of .03v while the engine was running at 3000rpm. Does this suggest my alternator is not charging the battery? Are there any other troubleshooting tests that I can make to find out? Battery is 3 years old, and had had very little use. Kept indoors over winter, and topped up with a charger every 6 weeks or so.
Any help appreciated.

 

[Bondo]

Hi all,
Have a 1989 Searay with a 3.0 liter merccuiser engine. For the last little while when under way the engine stalls...it restarts but always with a slugish battery turnover. I removed the battery and fully charged it to 13.7v. then returned it to the boat. I put a multimeter on the cables that go to the battery from the alternator, and got a reading of .03v while the engine was running at 3000rpm. Does this suggest my alternator is not charging the battery? Are there any other troubleshooting tests that I can make to find out? Battery is 3 years old, and had had very little use. Kept indoors over winter, and topped up with a charger every 6 weeks or so.
Any help appreciated.

Ayuh,..... Was the battery still on the charger when at 13.7v,..??
If not, I'm doubting yer meter,.....
A fully charged battery oughta be just over 12v,....

You should see 13.7v or so, with the motor running, 'n the alternator charging,....

 

[Scott Danforth]

if you are seeing a 0.3 volt drop on the wire between the alternator and the battery, you have crappy / dirty connections or a bad cable.

 

[1960 Starflite]

I'd suggest you put multimeter across battery terminals and check voltage while cranking.

 

[trooper1954]

Ayuh,..... Was the battery still on the charger when at 13.7v,..??
If not, I'm doubting yer meter,.....
A fully charged battery oughta be just over 12v,....

You should see 13.7v or so, with the motor running, 'n the alternator charging,....

Thx bondo,
Battery installed in boat with no charger attached reads 12.84v...when the stall happened, the motor did restart, but the turnover was very slow. When I returned to the dock after a 30 minute ride the battery read 11.2v....leads me to think the alternator wasn't doing its job. What should the reading be from the alternator to the battery if it's working correctly?
Thx

 

[Bondo]

Thx bondo,
Battery installed in boat with no charger attached reads 12.84v...when the stall happened, the motor did restart, but the turnover was very slow. When I returned to the dock after a 30 minute ride the battery read 11.2v....leads me to think the alternator wasn't doing its job. What should the reading be from the alternator to the battery if it's working correctly?
Thx

You should see 13.7v or so, with the motor running, 'n the alternator charging,....

 

[QBhoy]

Test the power at the battery when it’s running. If you’re seeing anything less than 13 something…