I need to replace my original thru hulls on my 76 32 ft sedan. Anyone know what size was used? Also, I have been reading about Maralon, which is not metal and is approved. Anyone used it before? Thanks in advance for any information as I am a Novice.

Boat US urges use of Marelon instead of ordinary plastic. For us aluminum can owners, it won't interact with any metal since it's a nylon and doesn't conduct electricity.

My thruhulls are still the original bronze, mounted through insulating blocks. This means that the hole I would get in the hull after removing one is NOT the same size as the OD of the original thruhull. So don't just measure the thruhull, measure the actual hole. My boat is just a year older than yours, so I imagine you have the same original bronze. Incidentally, mine are in fine shape and I see no need to change them.

Plastic thruhulls are fine above the waterline, but Marelon, which is one of those reinforced plastics, is necessary below the waterline. Crewboats either use a welded-in aluminum fitting, or Marelon.

I say "necessary" because you cannot pass a commercial survey with unapproved thruhulls. Same with wiring codes. It is best to keep everything approved for insurance and resale.

On my boat, the thruhull fitting itself is a separate piece from the shutoff valve - they are screwed together. I plan to replace the valves with 316 stainless ones, but will leave the thruhull itself unless it has some sort of problem. Let me know if you want a source for the valves.

Mike,

I bought 1" pipe 316 stainless ball valves w/ stainless balls. They are three-piece, held together by four machine screws with locking nuts. That way, they can be disassembled if needed. The original bronze ball valves are frozen, which is why I got the take-apart ones. I don't know if these are the right ones, any comment would be appreciated. They screw to the thruhull fitting using a plastic close nipple, and the water filters mount on top. It all looks original. I'll be installing them next haulout.

Doug

I don't know what the plastic stuff is that Marinette used for pipes but it sure is tough.

I haven't put these new valves in, and I might replace the thruhulls themselves with ss. I did not look at it last haulout - too busy scraping barnacles. Now there is a diver scrubbing my hull every month, let's hope it works.