Mercury rectifier wiring issue

[Tmacular]

hey guys. Just got a what I believe is a 1979 merc 70hp serial number 5356960. Motor runs great and has 148/150 in each cylinder! However the rectifier i found was fried. Now the way I got it the wires were off and I've only seen the 6 wire kind. I'm attaching some photos and just need help on what wire goes where. You can see from the photos my rectifier is toast

Thank you! I'm joining the mercury outboard club!

 

[achris]

That's not a Merc rectifier, and it looks like someone hooked the battery on backwards.

Follow this thread for all the info you need -> https://forums.iboats.com/forum/eng...connecting-rectifier-on-86-force-125-hp-motor

Chris........

 

[Tmacular]

Not a merc recitifer as in someone put the wrong one on? I ordered a new one that now has threaded poles. Was planning to switch the over to eyelit ends. Thanks for the post I was having issues finding one

 

[Tmacular]

I ordered sierra part number 18-5707 for a replacement from oreillys. Installing in morning thanks for the heads up I think I understand what you meant!

Thanks Chris!

 

[Tmacular]

Ok wait nevermind that post has the 2 2 and 1 wires. Mine has a blue and a grey/yellow together. And than a red. How's that work and where's the blue one?

 

[Chris1956]

Not sure what a 6 connection rectifier is. Mercury used a full wave rectifier of 4 diodes connected in a bridge configuration.

A Mercury rectifier will have 3 posts. The 4th connection is to ground, thru the rectifier body. Make sure the rectifier body is cleanly grounded.

The yellow/grey should go on one of the AC posts. There should be a yellow on the other AC post and the red on the + post, between the yellow wires.

 

[achris]

Not a merc recitifer as in someone put the wrong one on?...

It's not the 'wrong' one, it's just a properly priced one that didn't come from Mercury...

Merc rectifier good for about 10A, $60... Cheap old full wave bridge from Tandy (or whatever your local electronics shop is called), good for 35A, $3....

As an electronics tech, I can tell you the $3 item will do just as good a job as the $60 one. Just add the 4th wire (from the - terminal to a good ground on the engine block) and it's all the same.

That 'blue' wire, is actually gray, and it's your tacho feed.

Chris..........

 

[Tmacular]

Thanks Chris. Makes a lot more sense. So is my grey looking wire supposed to be brown? Ill install as you pointed out and report back. Red to positive. Grey/yellow are together so should I keep them that way? Put that on the ~ terminal and then attach blue to the other ~ and then ground and im good? Or should I separate yellow and grey to separate poles. I have to change the connectors out so I'm able to put them wherever they need to go.

Thanks again sorry I'm terrible with electrical I'm a plumber and we electric doesn't go well with water

 

[Tmacular]

what i meant by 6 wire I meant ive only seen the mercs that have 6 wires running to the grey rectifier style. The old 2 yellow 2 red black and whatever. U totally made that a lot simple tho ill report back when she's installed for approval

 

[Chris1956]

The two yellow wires from the stator (under the flywheel) go to the two AC posts on the rectifier. The grey (in 1979, it should be brown) wire is connected to either of the yellow wires. The red goes on the terminal between the yellow wires.

Not sure about blue wire. Grey wire is choke solenoid in 1979.

If the motor received a new wiring harness sometime in it's life it could have newer wire colors. In that case, the brown tach signal wire as replaced with a grey wire. The choke wire became yellow/black.

 

[Tmacular]

You're correct it is brown. It was dark and looked grey with my flash. Heres a photo of what I got working on stripping them now and just made a shrink tubed a new ground wire (was rotted and broke). Can I put the yellow and brown on their own eye lits and screw them together or do they have to be in the same eyelit. Thanks for your help Chris much appreciated!

 

[Tmacular]

This is what I have now!

 

[Tmacular]

Here's the new rectifer installed. However I'm not sure what to put the ground on? Is this correct? For the record my ring terminal is red. Thats not the red wire with the yellow .

I have blue on left terminal, yellow and brown on right terminal, red wire on positivr terminal. And the ground left but no terminal? Or is this merc rectifier grounded just by mounting it bc of thr metal backing plate mounts to metal

 

[achris]

The Merc/sierra rectifier has no terminal for ground. The ground is the base/housing of the rectifier. Just make sure the base and the screws are actually making good ground contact... And pull back a bit on the photos. That close they are hard to look at and work out what's going on.

Chris........

 

[Tmacular]

The Merc/sierra rectifier has no terminal for ground. The ground is the base/housing of the rectifier. Just make sure the base and the screws are actually making good ground contact... And pull back a bit on the photos. That close they are hard to look at and work out what's going on.

Chris........

Thanks Chris. It was operating today properly so I guess I did it correctly. I'm not sure how to delete my topic but consider this case closed

Cheers!