Krumbsnatcher

My buddy just recieved an 1998 Fountain Fever, he ran it to Catalina this last weekend and says his port motor tachometer is all over the place. He thinks he needs to buy a new one, I think he has a loose or corroded wire, what do you guys think?

What should we look for prior to buying a new tach, other than connecting the working tach to the tach in question?

Thanks OSO brothers.

Fountain38SC

Best guess would be a bad ground but i'm not an expert and this post was purely to get my 300th post in.

Gary Anderson

Ignition secondary problems (cracked/arcing wires, cap etc) can cause this. Worth checking before buying $100 tach. Hook a new tach to the coil or switch the tan tach lead wires at the dash.
Gary

Krumbsnatcher

He said the boat ran fine, and it did not seem to be missing, but I will have him check the cap.

thanks

mcollinstn

Most cheap-@ssed boat tachs (even the expensive cheap-@ssed ones) have a selector switch to tell the tach how many pulses equal a revolution. This selector switch cannot be sealed in lacquer like the rest of the electrical guts cause it has to be able to be switched. The contacts on this mother will oxidize and stop reliably conducting the tach signal to the coil inside the tach.

If you can "take apart" the tach, then do so. Mostly, though, you gotta break em to get them open. Before you break it open, hose some contact cleaner into the hole near/under the selector switch. Then move the selector back and forth a gazillion times, hosing every so often with the contact cleaner. After your arm is ready to fall off, hose some WD40 in it to give some semblance of barrier to future oxidation. Juggle the holy heLL out of the selector right on the correct setting. Try it. Betcha it works dandy.

If you don't really think you are getting contact cleaner on the right place by hosing blindly, then cut open the case where you can SEE the contacts. This is actually BEST cause you can carefully clean them, THEN smear liquid rubber or RTV or dielectric grease on it so it will NEVER give you fits again. You'll just have to glue the access hole up when you're done.

PS: it's a secret, but none of the marine gauges are really sealed cause they have to have a condensation drain hole at the bottom center of the case in the back... And DONT seal that cause it needs to drain..

Krumbsnatcher

Great posts guys and thanks, I will look at each of them tomorrow and let you know our findings.

It is 80 Degress and sunny today on the pacific!

WetKitty42

Mine is doing the same thing. I cleaned all of the connections, and it didn't do a thing.

mcollinstn

wet,

external connections won't cause a jumping tach. the INTERNAL contacts on the selector switch will/can.

Also, Snatcher made it clear thast the boat was a 98 Fountain. This means TBoltIV and Gaffrig gauges. Rules out a lot of other sources of trouble.

A points ignition will cause tach bouncing for a variety of reasons.
Some bargain brands of tachs are also disposable junk that need replaced from day one. What motor/ignition you running and what tach you got? Bounces on smooth water or only on rough water? Will it bounce at rest in neutral or only underway?

the more data we got the better we can diagnose it.

Mr Gadgets

Can you switch the wires from one tach to the other? If so you could rule out the tach or wiring or ignition..
Cut the circuit in half and see where the problem lies. Find the problem before you find a solution.. my .02 on troubleshooting.

Good luck