ST-60 THROUGH-HULL TOP DESTROYED

[keel_haul]

I just bought a used H-240 that had a Raymarine ST-60 unit in it. As I cleaned out the bilges I looked at the through-hull unit for the speed wheel. The top screw down ring that would hold the wheel unit down and water-tight was all black and split in half as though burned. My question is could a short in the twelve volt system have caused that? Could the unit have been hit by lightning?Has anyone else had this happen to their unit? The screw cap ring was some kind of composite. On my old boat those holding rings and the through hull were all brass. This unit does not seem to have a "stopper unit" as I had on my prior boat. It seems like a safety oversight. Had I launched without noticing the problem, a lot of water would have joined my crew.Have others replaced the screw hold-in nut with a brass one and added a brass stopper unit for safety?

 

[keel_haul]

another look at the hold-down nut/ring

My local marine electronics expert looked at my broken ring. He is certain that the 12 volt system would not have done it. I got a replacement ring and a Datamarine plug that goes in the hole when the speed wheel is out. It fits the Raymarine hole. The instructions for the plug warn that "Cleaners, gasolene, paint, sealants and other products may contain strong solvents, such as acetone, which can attack many plastics dramatically reducing their strength." I think the broken ring could have been ruined by a chemical. It did not smell burnt.