Likely the boat has a typical marine tach. There is an adjustment screw on the back. It should be set to the number "6" for a Johnson/Evinrude in order to count the alternator pulses from the stator. There should be a gray wire (left stubbed off by the factory) inside the control box for that engine. That's the tach signal wire. You will have to pull the control box apart to get to the wire. Draw the wire out of a small hole in the center of the bottom of the control box. It's possible that the trim gauge may function backward, if adapted to an Evinrude. You'll just have to hook it up to see. The fuel gauge is not engine-specific, so there is no adjustment there. I'd run all the gauges direct from the battery, not hook them up to any wiring in the control box.
