Tach acting up 1980 115 HP Johnson

[RickN]

When I start my boat up the tach works fine for about 5 minutes, then drops to zero and stays there. If I shut off the motor and restart it, it will do the same thing. I have checked the connections they appear to be ok and rectifier is new. Does anyone have any suggestions for troubleshooting this problem? Thanks!

 

[phatmanmike]

Re: Tach acting up 1980 115 HP Johnson

place a 1/2 watt 2k ohm resisitor between your send and ground terminals. any radioshack has these for $.99

 

[papastoy]

Re: Tach acting up 1980 115 HP Johnson

Rick, I had the same problem with 1991 225, turned out that due to corrosion in the tubing in the shaft that brings water all the way up around the voltage regulator it would get hot after 5 minutes and tach would get erratic and go to zero and stay there. Note , I never had an overheat problem with the motor and tell tale etc were fine, just wasnt enough water pressure to cool the V. reg and a hot V.Reg can screw up your tach.