Wacky Tachometer

[H2O]

For the past couple of years, my tach has been acting up. (GT 40). Needle bounced around randomly, sometimes registering several hundred or thousand RPM higher than it should, then returning to normal. Sometimes indicating an idle speed of 2000+ when the engine was idling normally. Checked wire connections to tach, no corrosion, tight. Thought tach was bad. Turned out the EFI sensors were dirty and sending error codes to tach! I used a different fuel system cleaner this summer (usually BG 44K - a great product). Tried "Ring Free" by Yamaha last week. Tach immediately became dead-on accurate with no bouncing needle and has remained that way. Would not have believed it had I not seen it myself! Thought I would pass this tidbit along.

[todicus]

RE: Wacky Tachometer

I have the same problem on my 95 gt-40........ where do you get the ring free product ? At a Yamaha dealer ?

[NautiqueJeff]

RE: Wacky Tachometer

You might also check to be sure that the tach is set to 8-cyl mode. You'll need to access the back of the gauge. Sometimes the setting gets knocked over to 6-cyl mode. That is a common problem for that date range.

[H2O]

RE: Wacky Tachometer

Ring Free is available through Yamaha dealerships. I happened to find it at G.I. Joes for $13.

[peteSki]

I have a similar problem on my 97 ski, tach all over the place. Since I installed Perfect Pass I haven't worried about it as the PP is working perfectly giving the correct rpm.

If I had the same problem as you with dirty sensors, wouldn't this also affect my PP rpm readings since it gets the rpm right from the back of the tach? If so, I'm guessing that my gauge would be faulty since the PP rpm reads correct but the gauge does not.

I wasn't aware of a switch on the back though, is it present on a 97 Ski with GT-40?

Pete

[DavidF]

IMHO, there is no way that using a fuel system cleaner will correct an erratic tach. I surmise that it was pure coincidence. Most likely, the contacts in the 4-6-8 cylinder switch are dirty within the tach.

[H2O]

MAP (manifold absolute pressure) sensor, in intake manifold, which causes oscillations in RPM when failing according to GT40 manual, is what I was thinking. May be a coincidence.

[nms1991]

The tach works off the signal from the coil which has no connection with the fuel system. It sounds more like your tach has a bad connection or it is on its way out. What year of boat? If it is a teleflex tach then it is probably the tach is on its way out.