I have a "classic" (i.e. old) boat with a 1991 135 HP Mercury Black Max. Last year, the RPM indicator stopped working ( it is getting power, as when ignition is off, it points to 900 RPM, and when on, it goes to zero. During last year's maintenance, the mechanic made it work again, and it was working until today. I assume it is a loose connection.
Anyone can point out where to look at?