2002 4.3 Voltmeter At 12v

[ajnader]

I Have A Searay Sundancer With Twin 4.3 Mercruisers. One Engine Has Dual Batteries And The Other One Only One, Both Have A Separate Battery Switch.
I Noticed That The Battery Gauge On The Engine With 2 Batteries Was Only At 12 Volts Even At Wot. The Other Engine Is Always At 14 Volts. I Replaced The Alternator And Keep Having The Same Problem, Sometimes You Can See The Gauge At 14 Volts But Most Of The Time Is At 12 Volts.
Yesterday I Installed 2 New Batteries And Crancked The Engine And Still Only 12 Volts.
What Do You Think May Be The Problem?
I Checked The Alternator With A Voltmeter And Is At 13.9 Volts But The Battery Is Only At 12.35 Volts.

Thanks

 

[hard-3]

Re: 2002 4.3 Voltmeter At 12v

you are saying that you checked it at the alternator and got 13.9 vts ,and from post to post on the batteries only 12 volts?
does not seem possible unless wiring open from alternator to main power terminal. or are you saying reading 13.9 volts at alternator and gauge in dash shows 12 volts? if that is case test voltage at back terminals of gauge could be bad gauge. voltage reading at battery posts should read same as alternator. if not look at battery cables for corrosion. I would think if voltage drop was that bad that it would not even crank over.

 

[tommays]

Re: 2002 4.3 Voltmeter At 12v

You have to check voltage at the battery with the meter and then follow the cables back to the switch if you not getting full voltage to see were your losing it

If both motors are putting out 13.8 volts at the batterys then they should charge and hold about 12.6 to 12.8 volts with the motor off


There can be many things onboard like the merc cathode system and bilge pumps that are connected dirrectly to the batterys and will run then down if the boat is not used enough OR does not have some type of shorepower charging system

 

[Bondo]

Re: 2002 4.3 Voltmeter At 12v

Both Have A Separate Battery Switch.

Ayuh,......

2 Dead On answers above Me,....

AJ,... Is the Switch in the right position,..??..??
Is it passing full voltage straight through,..??

As noted above,...
The boat should show the Same voltage All through the Whole system,.....

 

[ajnader]

Re: 2002 4.3 Voltmeter At 12v

checked batteiy switches and they are OK but noticed the following: after having the boat on shore power for a dayI checked the voltage at the batteries, at the switches and at the starting solenoids and it was over 14 volts all around. Checked the voltmeter with the starting switch on (engines off) and it was at 14 volts, took the boat for a sea trial and when I crancked the engine it took a couple of tries before the engine started, it sound like the starter was ready to fail. After the engine started the voltmeter was again back to 12 volts. what can be causing this? maybe something is draining the batteries?

 

[ajnader]

Re: 2002 4.3 Voltmeter At 12v

did some check this morning and found the following: the engine that is hard to start don't beep when you turn on the ignition switch and you can't hear the fuel pump crancking. the other engine beeps and the pump crancks. after a few tries the beep came off and the pump started pumping that's when the engine started. I noticed the fuel pump relay is clicking and assumed it was bad. removed the relay from the other engine, tried and still no alarm when starting the engine and no fuel pump noise. You have to crank the engine a few times before you can hear the alarm and fuel pump working and thn the engine will start right away.
Does anybody know what can be causing this?
took my service book and checked all terminals at the relay, everything was fine except that the volts at terminal 30 was at 12.5 volts with the ignition switch in the off posittion and drop to 10.6 with the switch on the on position.

 

[hard-3]

Re: 2002 4.3 Voltmeter At 12v

inspect all of the wiring for corrosion. if voltage is ok on shore power/battery chargers, then you are not getting output from alternater to battery . you said in previous post that alt output was ok . then check cable connection from alternator to starter battery cable connection. it sounds like the cable is off or corroded not letting alternator charge battery. look at all battery connections very closely, cables can corrode under the insulation and burn open without looking bad, pull on connections and wiggle to make sure everything is tight.

 

[ajnader]

Re: 2002 4.3 Voltmeter At 12v

Thanks everybody for the help, I finally founf the problem: the 90 amp fuse on the starter was burned so there were no connection between the alternator and the electric system in my boat.