mercury 150 outboard voltage regulator

[felderjr]

I have a year 2000 mercury offshore outboard motor. last weekend while 25 miles offshore we smelled some burning so we stopped the boat and took off the cowling. I found the lower of the 2 voltage regulators smoking badly and it then burst into flames. I used some pliers and unplugged all the wires from it and when it stopped smoking and cooled down, we ran the rest of the way back in with no problems. This is the 2nd time this has happened to me on this motor, once about 4 years ago and now, both times it was the lower regulator. I have a few questions, first, is there something that could cause this failure or do the regulators have a lifespan and need to be replaced as part of a preventative maintanence schedule. Second, why are there two and how is it that the boat ran flawlessly during the failure and after it was totally disconnected. Is one just for backup or does each regulator perform specific functions. Is the lower one under more stress than the upper causing it to fail twice in 9 years? The voltage guage has always shown about 13 volts at idle and 14 at higher rps and that did not change after the regulator failed and was disconnected. Any info I can get on troubleshooting this or areas on the motor that mey be causing this to check would be greatly appreciated as it is very un-nerving to be in the middle of the ocean and have smoke and flames coming out of the motor.

thanks in advance

Ric

 

[Chris1956]

Re: mercury 150 outboard voltage regulator

Ric, Those are two independent 20A charging systems. Perhaps there is some issue where the lower VR gets greater power from the stator, however, I do not know the design of the stator well enough to comment. You might replace with a CDI unit. They may be better than OEM.

 

[j_martin]

Re: mercury 150 outboard voltage regulator

20 amps through 14 gauge wire and bullet connecters is pretty iffy, and they often oveheat. I suspect the heat goes down the copper wires into the regulator and does some harm.

The newer black potted 6 wire regulators are better, and CDI is better yet. At any rate I solder and heat shrink the power connections to eliminate that trouble. Bullet is fine on the tach connection.

hope it helps
John

 

[felderjr]

Re: mercury 150 outboard voltage regulator

that does help, thank you.

ric