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Volt meter reading less then 12 volts

M

mkalink

New member
I have a 1986 260 hp mercruise

I have a 1986 260 hp mercruiser. I recently replaced the starter and now the volt meter reads between 10.5 and 11.5 reguardless of the engine rpms. Also the tach doesn't read the true rpm's all the time it will red line for a while then drop to zero then bounce around for a while maybe stop at the true rpm's then start the bouncing around again. The tach did this before the starter was changed.
Also at times there would be a whine coming from the alternator and the volts would jump up to 18 volts.
I changed the alternator this past weekend thinking this would solve the problems and it did eliminate the whine but the volts are still low.
Could I have a loose ground somewhere or maybe the voltage regulator gone bad.
I also replaced the batteries this year not because of the problems they were 4 years old and I don't want them to fail while I'm out fishing. 200 dollars every 4 or so years is cheaper then a tow.
 
"Michael:

I had a similar p

"Michael:

I had a similar problem 2 years ago w/my 87 4.3L. The tach jumped around and the voltmeter was not reliable. I changed both and they have been fine ever since. I actually changed all 7 gauges due to their age and appearence. I bought new Faria gauges on-line direct from www.GreatLakesSkipper.com. They came installed in a surplus gauge panel assy. for about $100. Dealers wanted about $500. Easy to remove and install in my boat.

Get a digital voltmeter. First clean and tighten all of the battery cable connectors at the batteries and the engine. Next take voltage readings at the alternator B+ terminal, starter and battery. Use the battery ground for all of your tests.

If you do it with the engine at idle, RUN THE BLOWER AND BE VERY CAREFUL NOT TO GET CAUGHT UP IN THE PULLEYS WITH YOUR CLOTHING AND TRY NOT TO SHORT OUT ANY TEST POINT! The alternator should be putting out between 13.2 and 14.8 volts depending upon the load. The subsequent voltage readings should not drop more than 0.02 volts from the alternator's reading. If the voltage drops more, you have a corroded wire that needs replaced.

I had to change my orange alt. output wire and battery cables and eventually rewired the entire boat due to corrosion. Good luck and safe boating."
 
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