Tachometer Won't Work

[scottt1020]

I took a 1992 75 hp Mercury off my boat and put a 1995 115 hp Mercury on it, and used the 75 hp wiring harness.

The 115 hp runs now but tachometer won't work. Is it the wiring harness? Is the 115 hp (runs on 2 cylinders until it reaches certain rmp, then 4 cylinders) not compatible with the 75 hp tach? How do you trouble shoot this?

Thanks, Scott

 

[oldman570]

Re: Tachometer Won't Work

The tach you have should work as it gets its signal fro the stator recitifer charging system on the motor. You will need to hook it to the stator wire for the new engine and will need a wireing diagram for the motor. 1manual,com has diagrams for newer motors and can be downloaded free. You have to have Adobie reader to get the downlosd, and will take some timeto download. If you still have the 75 you could look at the recitifer on it as to what you need to do to wire up the tach on the 115 as not much change was done to the systems over that time frame I belive.
Oldman570

 

[scottt1020]

Re: Tachometer Won't Work

Once I find the rectifer lead that goes to the tach, is there a way I can check that rectifer lead with an multimeter to make sure it's operating correctly?

Scott

 

[Barnacle_Bill]

Re: Tachometer Won't Work

Test your charging circuit.

 

[scottt1020]

Re: Tachometer Won't Work

thanks for the help guys.

Scott