Erratic Tachometer Reading

I have a 1998 Fishhunter with a 200 Mercury EFI. When I purchased the boat, the water pressure gauge did not work and the tachometer worked intermittently and also gave incorrecft reading when it did work. I was not able to find replacement matching gauges so I replaced the entire set of new Teleflex gauges. While the water pressure gauge now works properly, the tachometer is still giving me fits. I seems to work when it wants to until the motor warms up.

I am sure that all of the leads on the tachometer are attached securely and it does seems to read properly (at times) so I am sure that it is set on the proper pole. However, I do not know where these wires attach on the motor or if there is any other areas that would possibly cause this problem.

Any suggestions where to begin troubleshooting would be appreciated before I head the boat to the dealer for repairs.

Thanks

Since you replaced your tach make sure the settings are correct on the back of the guage for your motor. If thats good the only item left is your voltage regulators. You should have 2 of them on the back of your motor. There will be 2 grey wires coming off the regulators, one connected and the other plugged off. Those are the tach signal wires. First try switching the grey wires. If your tach starts working correctly then you know its your VR. If it does not fix it then you may have 2 bad VR's. Not an uncommon problem. Also check for darkened connections where the VR's connect to the stator. If they are burnt then the VR's are bad. When replacing voltage regulators always replace both at the same time regardless. Changing VR's is simple and straight forward. The Sierra after markets are about half the price as the merc parts.

Run the tach (gray wire) off the other voltage regulator. If that seemd to fix it, get you a couple of voltage regulators. You can change just the bad one, but better to replace in pairs.

Thanks for the suggestions. I will be sure to check those voltage regulators out in the next day or two.

Thanks Again.