I have a 1996 Nitro with a 75hp Merc

It was only 3 yrs old when I bought it; I think I remember the tach working in its early years but now I can't think back to the last time it really worked right.

 

The engine runs flawlessly; no skips, starts great, plenty of power. But the tach has always jumped around from 2k, then up to 6, then down to 3 etc...

Last year I noticed the volt meter showing it was charging too high. I believe the voltage output to the battery and tach reading, both, come from the rectifier; so I replaced it this spring with an aftermarket one. Same wiring as OE but not a genuine Mercury rectifier.

 

Now, the tach reads about 1k at idle but only goes up to around 2k at wot. It doesn't jump around like it did in years past, but definitely not reading correctly still.

 

Should I try and find a replacement tach or is there a diag tree someone could recommend starting with?

 

I recently replaced my prop and I am curious of RPM @ WOT to see if I have the correct pitch. Engine sounds like it's taching the same as last year but I'd still like the tach to operate properly.

 

Ideas?

The first thing I would try is to clean all the electrical connections. Especially the grounds. My 2010 tracker with a 90 hp merc was having issues with the tach and cleaning the connections solved the problem. 

^^^I'll start with that!

Thank you