on start up the tach goes to 7000 rpm and stays there

by Billy
(gainesville fl)

when I start up my 75 hp Yamaha 4 stroke the tach goes to 7000 and stays there, after a while it goes to what seems correct rpm, but on the next start up it goes to 7ooo, and when I turn the key off it goes to 0

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Sep 24, 2016
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tack switch corrosion
by: Bill from PA

I had a similar problem..... with the key on the tach went full scale. Was about to get new tach when I read on the internet that if the selector switch on the back of tach was not pointed directly at the correct marking (3 , 4 or 6 cylinder engines) the tach would read full scale. my switch was pointed at the correct setting but I immediately thought of corrosion......so I cranked the switch thru the full range of the 3 settings 75 times to clear corrosion on the internal contacts. The tach immediately worked fine. Note the boat had been used in a salt water environment.