Regulator/Rectifier, poor connection or just shot?

85 Century Palomino
170hp 3.7L Mercruiser

After doing some reading I figured my Regulator Rectifier was shot, I am generally only pulling 11V and some change while the motor is running at idle, underload over 1K rpm, and no load 1K rpm. I tested it with a meter as well at the batery and also only pulled ~11.3V. So while deciding if I was going with the alternator kit, or a new reg/rec I've been taking the boat out with fully charged batteies and running it. Last night, for a while I was pulling 12.2-12.4V according to both my fishfinder and my dash guage. It wasn't due to the fresh charge on the batteries, because when I first launched, it was only in the low 11s, but I went for a cruise part way through the night and it was kicking out a full volt more, even at idle.

I feel like I should be closer to 13 correct?

But what would cause the jump in a full vlot? Is it possible that I could take apart the connections clean it up and it would work? Everything looks clean, but you never know.

I'm just looking for some input on things that could be causing issues that would simmulate a bad reg/rec that I could go through and check out prior to spending the cash for replacement.

any input would be great, Thanks!

Re: Regulator/Rectifier, poor connection or just shot?

Sounds like a bad reg or bad (worn out) brushes.

If you have a low battery or a bad battery it will suck down the alt voltage, even if it is charging correctly. The reason is this: The altenator will put out as much current as needed to bring the voltage to near 14 volts, up to the altenator's maximum current capacity.

If it hits the current maximum before the 14 volts is achieved, then it will conitue to charge the battery at it's maximum rate. Slowly the voltage will increase until it hits 14ish. then, as the battery charges to full it will accept less and less current at the 14V level. If your battery is damaged internally then it may never get to 14 volts, and will be sucking up huge current which it will be converting to heat.


Chay

Re: Regulator/Rectifier, poor connection or just shot?

The majority of charging issues are with the voltage regulator. I replaced mine once, then when it failed a 2nd time I converted it to the belt driven alternator. No regrets.

There is a troubleshooting section for charging in the repair manual.

Re: Regulator/Rectifier, poor connection or just shot?

All the troubleshooting steps conclude with "replace the voltage regulator"