Wacky replacement tach

[oldslowandugly]

On a friend's boat the Teleflex tach quit, so he bought a new one and it wouldn't work either. I tested the old tach and it still worked fine. So I checked the wiring and found a probable tach signal wire break in the main engine harness as it exits the motor (1982 Evinrude 35 hp). Twisting and bending the harness made the tach work/fail. I suggested rather than opening the harness, just wiring in a new tach wire from the motor to the dash just to get through the season and he agreed that made sense. After that was done the tach works but the needle wanders and never seems to be reading exactly where it should. I inspected his job and noticed that he wound the new tach signal wire around the engine harness about 20 times, rather than tie-wrapping it in place. The battery cables are also inside this harness and I seem to remember that is a no-no as it introduces RFI which screws up the tach reading. Am I correct and will straightening out the wiring path solve this?

 

[glenn property of pam]

Re: Wacky replacement tach

plausable and intresting. i would have thought the pulses from the tach wire would have been more a pain on the other wires causing static on the radio etc but maybe you are correct. im sure when you fix the wire you will be able to tell us.
while you are there check to make sure the old tach wire is disconnect at both ends.

 

[oldslowandugly]

Re: Wacky replacement tach

Yup, that did it. I cut the wire, unwound it from the harness, cut it to the proper length, butt-connected it, and taped it straight along the harness. The tach reads fine now. Sometimes it's the simplest things.

 

[glenn property of pam]

Re: Wacky replacement tach

well spotted and its always good to learn something new