mercruiser alternator or battery problem

[betayv]

hi there I have a 1979 merruiser 228 305 my boat have two batteries, I have a battery switch, the battery switch have the option of battery 1, battery 2 or both, I went to start the boat and like always I put the swicth on both the boat start but I notice my alternator gage only read 11.5 is below 12v, before used to read 12-14, when I flip the switch to battery 2 and motor died, I check the battery 2 and is dead, my battery 1 is good, I went and replaced both of the batteries I didnt install the batteries yet but the alternator gage have me thinking probably the cage read below 12 because the battery 2 was dead, Im sorry if my questions is dumb but you guys think my alternator is shot or just the batteries.

 

[Maclin]

Re: mercruiser alternator or battery problem

I think it is just the batteries. A dead battery will definitely affect the voltage reading even if there is a good battery in parallel with it.

 

[chiefalen]

Re: mercruiser alternator or battery problem

A dead battery will draw down the good battery and eventually kill it.

I never try to charge both battery at the same time anyway, i use one at a time and sometime on the water i switch it over to charge the other one.

On the way out 1 battery on the way in the other .

 

[Bondo]

Re: mercruiser alternator or battery problem

but I notice my alternator gage only read 11.5 is below 12v, before used to read 12-14,

Ayuh,...

I think your Charging System Isn't Charging....

Even with Dead batteries,...
A running motor should be showing 13.6 Volts...

That's why it wouldn't run on the Dead battery,... There's No Charge for it to run on....

 

[abj87]

Re: mercruiser alternator or battery problem

The boat should continue to run even with a dead battery connected or no battery for that matter.
Alternators are easy to check.
Measure voltage at battery with engine off. should be around 11-12 volts.
start engine, bring rpm to 2000, and check voltage again, should be in the range of 12.5-15volts.
your looking for a rise in the battery voltage. Use a DVM right on the battery, i never trust the dash gauges.

 

[chiefalen]

Re: mercruiser alternator or battery problem

Autozone will check that alternator for free. Thats my2 cents let them check it.

 

[betayv]

Re: mercruiser alternator or battery problem

hummm I think my alternator is shot tomorrow I will install the batteries and start the motor and check with a voltimeter I will let you guys know.

 

[chiefalen]

Re: mercruiser alternator or battery problem

Marine one please.