96 40HP Merc bad rectifier/regulator

[jcnhwildcat]

Something burned out in my 1996 40HP Merc (4 cyl), I believe this is the rectifier/voltage regulator (see below)? Had trouble with the tach cutting out (more often not working), could that have been an indication of an impending problem with the rectifier? Also, I installed a Blue Sea Systems Dual Battery system before the season started and probably put 50-60 hours fishing (trolling with the outboard and bass fishing w/ electric motor) before this happened. If I did the install improperly, would it have gone this long before burning out the regulator? Though I've heard this is a common problem with Merc rectifiers.

 

[Bass Tracker TX17]

Re: 96 40HP Merc bad rectifier/regulator

I just replaced mine but it didn't look like that.
Had a voltage spike for 30 seconds and then the tach went down and didn't charge
They have changed the part number like 5 or 6 times since 96.
With 50 or 60 hours combined with the Dual Battery system i doubt that would cause your condition however it would not hurt to double check your installation and check your batteries
About 2 days later after repair i started getting a fowling #1 plug. Never did that ever in 12 years of owning it. Had to replace the #1 coil and resolved that problem. A coincidence I'm hoping....

Mike

 

[jcnhwildcat]

Re: 96 40HP Merc bad rectifier/regulator

Ok, going to replace the rectifier this upcoming weekend, got the new one at the shop last weekend. All the wiring matches up between the new one and old one, except... the new one has an extra black wire with a ring connector versus the bullet-type connectors on the other wires. Intuition tells me a ground connection, given the color. Thoughts? Why would the old rectifier not include that extra wire?

 

[Bass Tracker TX17]

Re: 96 40HP Merc bad rectifier/regulator

correct.
they updated the reg like 5 times over the years. The extra black wire goes to ground. i put mine with all the other ones in the stack.

They might have realized a loose mounted reg. would have a bad ground and cause issues. just a thought. But anyway it's a plug and play. Make sure all your other wires are ok.

 

[j_martin]

Re: 96 40HP Merc bad rectifier/regulator

The old clear potted one you burned up is known to be weak. The new one is better. The black wire is a reliable ground. The frame mounting screw wasn't.

The iffy tach was the standard harbinger of bad times coming for the regulator.

Put it in and enjoy your boat.

hope it helps
John

 

[jcnhwildcat]

Re: 96 40HP Merc bad rectifier/regulator

Great, thanks to everyone who has offered their feedback!

 

[lilmandavis]

Re: 96 40HP Merc bad rectifier/regulator

I would also recomend a dual battery isolator. They are very easy to install and keeps some strain off your engines charging system as well as keeping everything else happy on the engine electronic wise. The isolator sees different voltages in each of the batts not as a group. where one is half down from trolling the other might be full. put a load on the good one and the trolling one might be enough of a draw to burn some wires. I had a prob like yours and a isolator and batt selector switch cured all. And then on top of that a can of corosion X is still my best friend on everything mechanical and electrical to.
Kinda like dont put a new alternator on your car with a half full batt.

this page is a great help for troubleshooting with little equipment on charging and ignition systems

http://outboardparts.com/mercury/miscellaneous/troubleshootinghelp.htm

 

[jcnhwildcat]

Re: 96 40HP Merc bad rectifier/regulator

I could be wrong, but I thought my dual battery system (Blue Sea Systems 7610 Automatic Charging Relay (ACR) and 5511e Dual Circuit Plus) enabled me to isolate the batterys while the relay monitors the individual battery voltages. But hey, if I need to install another item, so be it. Thoughts?