Voltage issues with 350 MercCruiser

[zacheus007]

I have a Mercruiser 350 in a 23ft Penn Yan and I am having issue with the Battery losing voltage. I am running dual marine batteries and I cannot keep the voltage up, I end up taking one battery off and charging it and as you could imagine it is getting old.

I typically troll with my boat with throttle at the lowest setting, with the boat just in gear pushing at 2-2.5 mph. If I do this about every half an hour the voltage will drop a .1. When I first got the boat it would run at a consistent 12.1 but now it runs at about 11.9-12 and when trolling it runs at 11-11.3 and it will dip down to as low as 10.5. The only thing that has changed is that I installed a GPS/Sonar Unit and a marine stereo. I know that the stereo will trickle off the battery but it was my understanding while the boat was running the alternator would charge the batteries?

Does anyone know of any sites that I can resource for this or anyone have had similar problems, and/or diagnosis for this issue?

Any and all help is appreciated!

Best,

Zach

 

[gcboat]

Re: Voltage issues with 350 MercCruiser

Sounds to me like your alternator is getting tired. What are your volts when running at a higher RPM ?

 

[zacheus007]

Re: Voltage issues with 350 MercCruiser

High RPM they are running at 12 consistently short spurts of 12.1-12.3.

Is there any ways to test what voltage the alternator is pushing to the batteries?

 

[bomar76]

Re: Voltage issues with 350 MercCruiser

Yes.
Buy a cheap digital volt meter ($3 at Harbor Freight) and check voltage at the battery at various RPM's
Do not rely on the dash gauge.

 

[rock_doctor]

Re: Voltage issues with 350 MercCruiser

You are looking for something in the 13.8 - 14.2 range with the engine running. A fully charged battery will give you ~12.6 volts.

 

[Bondo Again]

Re: Voltage issues with 350 MercCruiser

Ayuh,..... Your charging system is Whooped....

It could be the Alternator, or it's Wiring......

As noted,... With the motor running,... You should be seeing 13.6Vs.....

 

[zacheus007]

Re: Voltage issues with 350 MercCruiser

Looks like I will be chasing wires with a voltage meter this week. Fun, Fun. I will let yall know what I find. Thank you for your help.

 

[zacheus007]

Re: Voltage issues with 350 MercCruiser

That is interesting, the belt has squealed twice upon starting but I did not have any sqeauling after using this weekend. I definately check that first.

 

[zacheus007]

Re: Voltage issues with 350 MercCruiser

Simpe fix, which usually doesn't happen to me. I went to start it and I noticed a little smoke. I happen to have an electrian on the boat and he advised me that smoke is usually a loose ground and all of my power is being lost through where ever that smoke is coming from. We checked a fair amount of grounds looking for heat and found two that had bad connections. Cleaned the connections and since then my boat has been working much better.

The volts are still a little low but I think that is because the batteries are a little weak from getting drained.

It would seem that the batteries have a tough time getting the engine to turn over and then once it gets those first couple turns, it turns over and starts just fine. Now I have to find out why it is turning so slow on those first turns.

I am finding that boat ownership is always something, but it is interesting learning all these new things. Thanks for all your help!