My 3.7 mercruiser overcharging - help please.

[boltonranger]

First let me say this forum is invaluable to folks like me.
I am a shadetree guy; and have been able to repair my engine and boat because of you fellas.
1988 Stingray SVB 176 ; 3.7 merc I/O Alpha One
So here it is.
First trip out 2 weeks ago. I had drained out the old gas from my tank; put in fresh (although all had stabil)
and fired up the boat at the launch. Mechanical fuel pump needed time to crank the gas in the line and before I knew it my battery was wheezing and quit. Kind fellow at the launch helped me. First by handing me a spare battery to lay on deck and connect to mine with jumpers. Not enough juice. Next he fires up his boat and jumps mine to life. All good I thought.
Noticed as we were out that the battery still was slow to crank. Since my boat is fairly well tuned it would fire up.
So between then and now I bought an AGM starting battery since the old wet cell one was at least 6 years old.

OK so went to go out this weekend and figured test on muffs first couldn't hurt - So I started the motor and noticed 17 volts on my panel gage. Hmm. So I got my electrical meter and tested running and off. 12-13 volts with engine off. 17.6 while running at idle; engine warm now. No smoke / electric smell; just higher than normal voltage. Nothing bad looking over at the regulator on the block by the way.


I'm thinking I did my system harm by jumping... would you agree?
Wondering if regulator is shot and it's time to replace or buy a kit and retrofit.

Some questions:

I've seen an aftermarket watercooled regulator online for a little less than the merc one.
It says right at the top of the web page "Do not use with sealed battery or AGM battery."

I did not notice regulator trouble until I installed the new agm battery and ran on muffs - Coincidence?
Did I kill the regulator with the jump at the launch or the new battery?
Should I assume the No AGM also follows for my existing Merc regulator?
Should I throw the old battery back in and check charging voltage?
Is there a procedure to bench test my existing regulator?

I charged the new AGM battery the night before.
Incidentally I did not notice high voltage out on the water the last time out.
It may have been - but I did not notice.
So time and money being what they are I'm turning to you guys for help.
Can you answer my questions?
Thanks.
-br

 

[boltonranger]

Re: My 3.7 mercruiser overcharging - help please.

Another question:
I found this external Marine regulator online.
http://www.autozone.com/autozone/ac...regulator/_/N-269e?itemIdentifier=319661_0_0_

Could this possibly work for me?

I have read the lively "Can I use a $38.00 Ford regulator?" thread and don't want to pick a fight;
Just looking to learn and understand... be gentle.
-br

 

[stonyloam]

Re: My 3.7 mercruiser overcharging - help please.

Overcharging seems to be an indicator of a bad voltage regulator in the 470. Forget the new regulator, go with an alternator conversion like the one from Breezeworks (http://www.breezeworks.net/). IMHO I would not try the ford regulator, too many unknowns. I do not believe that jumping the battery (assuming that you did it correctly) would harm the regulator.

 

[wrestling coach]

Re: My 3.7 mercruiser overcharging - help please.

Move on to the Breezeworks conversion and don't look back. Here is mine installed this season. Low mount no power steering worked best for me. Everything fits. Great wiring harness and instructions.

Dennis

 

[muc]

Re: My 3.7 mercruiser overcharging - help please.

Most of the 3.7L over charging issues I have seen are the stator starting to short to ground.
Might want to get an ohm meter and check that first.

 

[natemoore]

Re: My 3.7 mercruiser overcharging - help please.

My 470 was outputting 17 volts too. I did an alternator conversion kit two years ago. That's the way to go.

 

[generator12]

Re: My 3.7 mercruiser overcharging - help please.

The only way to harm a charging system by jumping is to do it with polarity reversed. When you do that, you'll likely blow the diodes in the receiving system.

As everyone who has responded says, you've likely suffered a failure of the voltage regulator. Clearly, the fix is a conversion to the external, belt-driven alternator. The guys mention Breezeworks. I agree with that. If you need a high-mount, look up Hunn-Finn.

My 470 was in the sixteen/seventeen volt range like yours, and I converted it. Not too bad a job.