Tach Issues

Ok so it has come to my attention that i might have a bad tach. My tach runs at 6k RPM at wot with a 21 pitch prop. The all knowing and all powerful frank stated that my little Chrysler 85HP should even come close to running that fast. SOOOOO, my question is, how do i trouble shoot this? Should i just replace the tach, the rectifier, or both? Thanks guys

Re: Tach Issues

Do you have a Motorola ignition a Big Black Box or a Prestolite ignition one coil for each spark plug? If your tach is set to a different setting (on the rear of the tach there usually is a selector) or its wrong tach you could be getting bad readings from that. For a Motorola it needs to be of the 12 point type and for the prestolite i think it needs to be a 20 point. Now if it used to work and now doesn't testing the rectifier should be easy enough (i would say all it needs to do is charge for you to know it is working) i would look at the repair manual and see what they recommend for testing the rectifier. The fact that you are getting a reading seems like it is working to me, but I am in no way an expert.

Re: Tach Issues

Hmmm good point, i checked and the tach is set on 20 pole like my ignition system recommends and also my battery is being charged at 14 volts per volt meter at wot. So seems to me my recifiier is working and i could just have a bad tach.

Re: Tach Issues

thanks for fast response on my lower unit oil question, my 93 capri 18' does not have a tach, did yours from factory or is it after market, just wondering becouse i thought it was odd for mine not to have one, but it is on my list of things to do

Re: Tach Issues

My bay didnt have a tach or a volt meter, i added both after market. Best investments ever, as you cant prop the boat right with out a tach, and the volt meter lets you know if your charging system works not to mention life of the battery. Other thing i would suggest is a tell tale, there is a sticky threat at the top of this thread, read it, cheap to do and great piece of mind. Worth the effort.