Over voltage charging on 4.3 OMC

[ulster1]

I have twin 4.3 omc 1986 with cobra drives.
During prep for the water this year I had the batteries checked at a reliable source they indicated on was in sad shape so I bought a new one same cca etc.
Upon install I wanted to ensure correct voltage to the system so I turned on my fish finder and inverter which both show the voltage.
The high voltage alarm went off on my inverter and when I checked my voltage it was up at 15.9 fluctuating up and down between 14.8.and 15.9.
It is not consistant some times when I start the motors it runs ar 14.8 of a few minutes 10--15 then starts to fluctuate between 14.8 and 15.9 again.
I removed the alternators and had them checked by a marine shop and they ran at 14.8volts on the test bench the shop indicated this was ok??
I am now in a position wher I do not want to take the boat out until this has been resolved.
I have checked the connections to the batteries and they are solid I have a switch so that I can run on batt 1 batt 2 or both How can I determine what the problem is.

Thanks in advance for help.

 

[HT32BSX115]

Re: Over voltage charging on 4.3 OMC

Howdy,

I took a look at my OMC service manual (it's for an 87 Cobra) And for a motorola ALT the voltage should be 13.0-14.7 VDC.

It goes on to say that if battery overcharge is indicated or alternator indicates 14.7 V (no load), with the engine idling, the voltage regulator is shorted and must be replaced. (it appears that your regulators are inside the alternators.

It's difficult to say whether you still have Motorola alternators on an 86 boat in 2008.

OMC has a specific test procedure that involves connecting a load bank across the battery and running the engine.

You then connect an ammeter and voltmeter to the output of each alternator and operate the engine at idle, 1500rpm, and 3000 rpm to check output (under load).

There's other tests that are somewhat lengthy to type out here. A lot of automotive alternator checkers do not load the alternator to it's max load.

Sometimes a poor or corroded ground connection can fool a voltage regulator into running the alternator at max output.

Check/clean all your connections, including the main harness plug on the engine(s)

Get yourself an OEM OMC service manual too.


Cheers,

Rick

 

[JustJason]

Re: Over voltage charging on 4.3 OMC

You need this a DMM, an amp clamp, and a battery load tester like this one

http://www.sears.com/shc/s/p_10153_12605_00921019000P

to get it figured out....

If you don't have all three your just gonna end up throwing parts at it.

 

[ulster1]

Re: Over voltage charging on 4.3 OMC

Thanks for the info Guy's.

Will post when I get it repaired.

 

[ulster1]

Re: Over voltage charging on 4.3 OMC

OK got my hands on the DMM, amp clamp and the battery load tester,
Can you walk me through the steps I need to take to determine if the fault is the alternators batteries or the wiring.
I done more testing before getting the above equ. here are the results.
With selector switch set @ #1 battery I started the port motor 15.8v
With selector switch set @ #1 battery I started the star motor 15.9v
With selector switch set @ #2 battery I started the port motor 15.8v
With selector switch set @ #2 battery I started the star motor 15.6v
The only difference between winterising and spring start up is the new battery?? I am at a loss with this. I can't see both alternators failing @ the same time or the wiring on boath motors failing @ the same time.

Thanks for any help

Ed

 

[JCF350]

Re: Over voltage charging on 4.3 OMC

Is there a dual alternator controller on your boat?

 

[ulster1]

Re: Over voltage charging on 4.3 OMC

Do not know what a dual alternator controller looks like can you give me a description.

 

[JCF350]

Re: Over voltage charging on 4.3 OMC

One example.
http://balmar.net/page21-centerfielder.html

Judging from your voltage readings your Alternators are fine. Looks like they are getting to much voltage to the field windings and full (or close to) fielding the windings. For what ever reason?

 

[bruceb58]

Re: Over voltage charging on 4.3 OMC

Do these alternators have remote sensing and are the sense wires connected to a battery?

 

[ulster1]

Re: Over voltage charging on 4.3 OMC

Update,
The alternators have been rebuilt and are now charging OK.
The 1 st shop I took them to gave me incorrect readings,