Tachometer 1977 85hp Johnson

[kevin2011]

Ijust put in a new tach and have the setting on 6p. At idle it's at 600 RPM's, as I throttle up the tach drops off line at about 1500 RPM's. Any ideas what the problem is?

 

[wilde1j]

Re: Tachometer 1977 85hp Johnson

Possible failing tach, or the sw that sets the pulses needs to be cycled and carefully returned to 6P. Sometome the sw will be between settings and cause flaky action. Also. check the tach wiring for loose or high resistance connections.

 

[kevin2011]

Re: Tachometer 1977 85hp Johnson

So do I need to re-set the switch while the engine is running or off. The tach is new and the wiring is new throughout the boat. Thanks for the help really appreciate it.

 

[HighTrim]

Re: Tachometer 1977 85hp Johnson

I would start by testing the rectifier myself. You do not want to be running with a faulty rectifier. Usually the tach will just not work with a faulty rectifier, but have seen some strange things happen, cannot hurt to test. Do not need to reset switch while boat is running.

 

[Barnacle_Bill]

Re: Tachometer 1977 85hp Johnson

I agree with HT, check your rectifier. It all depends on how the diode(s) blow as to how it affects the tach.

 

[kevin2011]

Re: Tachometer 1977 85hp Johnson

I checked the rectifier and found part of the wire covering was worn off and exposed the wires. The wires appeared to be exsposed for sometime. Thanks for the help.