I recently removed the tachometer from my 89 Cat 30 for testing. When I returned to the boat I found that my bilge pump and other accessories were not working. Further investigation showed that disconnecting the tachometer had broken the ground circuit for the main distribution board. Before I started rewiring the ground circuit I wondered if anybody else has had this experience. Is this the way Catalina built the boat or has somebody rigged it? When I replaced the trailer plugs i noticed 2 extra wires.