alternator trouble 1995 225 merc

[Sea Hawk]

I just replaced my marine batteries and decided to check my alternator voltage output just for the **** of it. I was supprised to see that it was only putting out 12.9 volts. I then tested the batteries. They also were putting out 12.9 volts. Having access to lots of parts, I tried another alternator. The same results, 12.9 volts. My shop manual states that the alternator should put out 13.5 - 15 volts. could the problem be somewhere other than the alternator it's self. or is it just ok for it to put out 12.9 and don't worry about it.? Any experienced help would be greatly appriciated. Just want to know if the alternator is working and charging these two new batteries at 12.9 volts, or are they just very sowly draining the power from the new batteries?

 

[wilde1j]

Re: alternator trouble 1995 225 merc

You need to use your shop manual, first of all.<br /><br />Does your motor have a rectifier/voltage regulator? If so, measure the input voltage to the rectifier (it will be AC and should be ~ 20 vac at idle). You really need a manual which will point you to where to measure with a VOM.<br /><br />Shop manuals I've used give a flow chart type diagnosis path, which will get the problem doped out quickly (most times).