1983 model johnson 175 hp the problem is this at idle speed to say 1500 rpms tach will work fine, as i increase speed of engine to WOT at around 3500 rpms my tach goes to zero reading if i slow down sometimes it will correct itself but most of the time now it wont. i have to turn motor off and re crank it and the cycle starts all over again.have checked all connections and they seem to be fine what do i need to do is the tach just failing???
