1995 Merc 115 rectifier?

[David Stone]

I have discovered I have a bad recitfier on my 1995 Mercury 115 hp (tach stopped working and voltage does change, go up when motor is running). Now the 2 big questions: Where do I find this bad rectifier? Is it the square black box (approx 2" x 2") on the side of the motor from which the grey tach wire comes? Where do I get a good price for a replacement??

Thanks for your help.

 

[Chris1956]

Re: 1995 Merc 115 rectifier?

David, If your battery voltage rises as the RPMs increase the rectifier is at least charging somewhat. The Rectifier is a black piece of plastic with three connections with nuts holding two yellow stator AC wires and the red battery cable. The grey tach wire should be connected to one of the yellow stator wires. It is possible that only 1/2 the rectifier is bad. if you switch the grey wire to the other yellow wire, and the tach works, the rectifier is 1/2 bad (and 1/2 good).

Replacements are avail from Merc, Sierra, maybe GLM and at electronic shops or Radio Shack. The first three are direct replacements, the RS component will require a change out of the ring terminals to spade terminals, but is a much cheaper and much superior device.

 

[David Stone]

Re: 1995 Merc 115 rectifier?

Chris1956, Thanks for the quick reply. I have heard of the Radio Shack replacement. Could you tell me the part I should ask for? I realize I would need to cut off the ring terminals and replace it with spade to fit. Anything else I need to know or do??? There is no increase in voltage with the motor running and no signal to the tach. I have not tried switching post, will a half a rectifier work?? Should I worry about the sator???

Thanks in advance.

 

[Barnacle_Bill]

Re: 1995 Merc 115 rectifier?

Here is the procedure for testing that rectifier.

Testing Merc?s square rectifier

If you use an analog meter set it on the RX1000 scale.
If using a digital meter, set it on the diode symbol.

1. Disconnect the battery leads.
2. Disconnect all wires on the rectifier.
3. Connect the red test lead to ground and the black lead alternately to terminals A and C.
The meter should show continuity.
4. Connect the black lead to gound and the red lead alternately to terminals A and C.
The meter should not show continuity.
5. Connect the black lead to terminal B and the red lead alternately to terminals A and C.
The meter should show continuity.
6. Connect the red lead to terminal B and the black lead alternately to terminals A and C.
The meter should not show continuity.
7. Replace the rectifier if you do not get correct readings.