You can try replacing the harness but you are just going to take one bad apple out and put another back in the basket. Solutions assuming your starter and batteries are not an issue are... a relay, and a start button in the engine bay. What I did has worked wonderfully and is easy to do. I went to the local marine exchange and got 20 feet of 6 gauge braided, tinned wire and a 30 amp wire inline fuse. To install I pulled out the instrument panel and connected to the male lead on starter button. Then I fished it down through pedestal, and through the wire entrance (pull up your floorboard that houses rudder cables) in port lazarette. Go down below and pull out your back wall. Just remove the panels covering your stuffing box, exhaust and then gently pry it out. Its a wonderful thing on the 336. Feed the wire down into the alley between your gas tank, and holding tank. Run it right along your existing ignition wire and hook it to the solenoid (after fusing it). I left the old harness still routed but unhooked for emergencies. Now check the voltage at the solenoid with the key on. Volts will still be 12+ and she will start now.. now.. now. Total cost under $30. And I think a good fix. Even a caveman could do it. I included the best picture I have of the aft wall. The vertical piece of wood is the outer edge of the wall that comes out. Cheers Ricks/v Whiskey Chaser