1994 135 HP Mercury Reisitor Question

[Alpinegold]

I have a 1994 135 hp Mercury Black Max that is on my 17' Pro Craft. On the very back side of the motor are 2 circuit board looking boxes. I traced the wiring diagram and I think one of them is the resistor or rectifier. A couple of the wires are chared. The circuit board boxes have a cover on them and it looks like on one side of the board is chared . It looks discolored black. In addition my tach does not work.

Is this a rectifier or resistor? How can I test to see if it is bad? What problems will this cause? What could have been a probable cause of it going bad ( if it tests bad ) ?

I have the Clymer manual and a Beckman HD 100 meter.

I can still get about 50 MPH. There is one issue that I do not think is related. I get a thumping sound from the lower unit when coming out of the hole but when I get planed it goes away.

I am trying to tackle one problem at a time and any help I can get on the first issue would be really appreciated.

Thanks,

Leslie

 

[Alpinegold]

Re: 1994 135 HP Mercury Reisitor Question

I have one correction to my question. I believe the 2 circuits boxs I am refering to is the Rectifier and the voltage regulator instead of a resistor. This is per the wiring diagram in the Clymer book.

 

[Chris1956]

Re: 1994 135 HP Mercury Reisitor Question

Leslie. Those two devices may be the twin 20A voltage regulators. See if you have four yellow wires coming from under the flywheel, two to each device. If so, that is what they are. Other year motors had a single 40A VR.


The grey wire on the upper voltage regulator provides the signal to the tach. If the upper VR is bad, the tach will not work. You may switch the grey wire to the lower VR (add and extension), and it the VR is good your tach may work.