Tach on Thunderbolt Merc 500 `74

[GonzagaCRO]

I need advice about connecting the tach to my merc 500 `74.

I recently bought a new Teleflex tach and connected it to controls plug but it won?t work, everything is correctly connected, pointer moves to 0 rpm when the ignition key is switched ON.
I searched and found that I have to remove the wire from switchbox and connect it to rectifier.
Is this true? Can I damage something?


Here are some pictures;

Igor

 

[GonzagaCRO]

Re: Tach on Thunderbolt Merc 500 `74

Bump

 

[OCboat]

Re: Tach on Thunderbolt Merc 500 `74

You have the type II ignition with the lightning energizer driver. It is a different type of ignition than most of the older mercs. You can either run a separate wire all the way from a yellow terminal on the rectifier to the back of the tach or you can try this. On my internal wiring harness I have a orange wire that comes from the harness and connects to the switch box. There is also a second orange wire coming out of the internal harness that is connected to the first orange wire somewhere between the harness and switch box. Mine was all wrapped up in electrical tape and I had to peel back the tape to expose the pig tail where the two orange wire became one. I then separated the two orange wires and let the one continue to run to the switch box and the other one I ran to a yellow terminal on the rectifier. You can now use the harness at your control box to run your tach. Here is a link with a few pictures. It explains it pretty well.
http://forums.iboats.com/showthread.php?t=182839&highlight=lightning+energizer

 

[GonzagaCRO]

Re: Tach on Thunderbolt Merc 500 `74

2OC;

Thanks a lot! I will try it and I will post some pics about it.
There are 2 yellow wires connected to rectifier, which one is the right one?
One to the right or one in the middle?

Best regards,


Igor

 

[OCboat]

Re: Tach on Thunderbolt Merc 500 `74

Either yellow one, just not the red. Looking forward to the pictures. It doesn't seem that there are too many people who have this type of ignition on their motors.

 

[GonzagaCRO]

Re: Tach on Thunderbolt Merc 500 `74

A little update from last time;

I follow OC`s instructions and now tach is working!

I have removed the black tape around the wires and as OC said there are two wires, salmon and brown fused together and connected to switchbox.

Just remove the brown wire and connect it to the rectifier.

TNX once again OC!


Best regards,


Igor

 

[OCboat]

Re: Tach on Thunderbolt Merc 500 `74

Good job and nice pictures!