Re: 1985 Johnson 90HP OB install tachometer?
You will need a marine tach. Any of them is adjustable and can be set for your specific engine. There should be a pigtail wire at the control box which is there for the addition of a tach. It may be dangling there with three wires and a black plug. The grey wire is the signal wire, red/pink is hot and black should be ground. You can run wires from the pigtail to the dash and connect them to the tach. If your control box is an older one, it should have a single grey wire folded up and left loose inside the control box itself.
