Thru-hull removal

[Chuck Fort]

I am trying to remove the thru-hulls for the head intake, engine intake and the galley sink drain. I have successfully removed the first 2, but am having a hard time with the sink drain. I can get a pipe wrench on the inside, but not enough leverage to turn. The outside is a mushroom style, and I can't get a bite with the pipe wrench. Any suggestions???Chuck Fort"Caduceus"1983 H 27

 

[Don Alexander]

Key for Outside

Chuck,Most through hull fittings have either a place for a key to fit (plastic through hulls) or some cast in webs against which a suitable piece of metal can be brought to bear (bronze fittings).Normally these are intended to resist turning whilst the fitting is being tightened on installation.Suggest you look into making a suitable metal key, though your chances of unscrewing the fitting from the outside are small as the sealant will stop it from rotating.Best not to butcher the fitting as a new one may not be identical.Merry Christmas.

 

[JayT]

BoatUS has a pamphlet in their stores describing thru-hull removal.JayT

 

[Garry @ S/V TASHTEGO]

Thru Hull Removal

A bronze mushroom-head thruhull will usually have two tabs or bumps on the inside of the bore. Anything that will jam on those tabs will hold the thruhull steady while you remove whatever is fastening it on the inside. If you have somebody on the outside to hold the thruhull you can work on the inside. If you are working alone it is helpful to have the valve off so that you can stick you jamming device down the thruhull from the inside while you remove the fastener. Even if there is a seacock or a ball valve you should be able to pass the jammer thru with the valve wide open. If you have a nut on the inside of the thruhull you will have to unscrew it. If you have already put a pipe wrench on the threaded part of the thru hull and chewed up the threads you will have to unscrew the nut as far as you can then cut the thruhull off with a hacksaw. This will probably be easier if you unscrew the nut as far as you can then push the thruhull out through the hull as far as it will go and saw from the outside where there is a lot more room. I made a jammer by finding a socket that just fit into the bore of the thruhull and grinding notches in it to fit over the tabs. If you can't turn the connection on the inside with a pipe wrench a larger wrench won't help as there is so little room. I found a hammer applied smartly to the wrench handle to be successful in removing the nut.When it come time to put in a new thruhull you should put a proper seacock on it not a ball valve or a gate valve. There is a post from me in the archives about how to do it right. There is also a pretty good discussion in Nigel Calder's book, "The Boatowners Mechanical and Electrical Manual."

 

[John Keane]

Worst Case Scenario

i have had to grind the mushroom portion of the fitting off with a 4" angle grinder, with a fibre disk. you must be carefull not to apply too much heat so you dont damage the surrounding gelcoat and fiberglass. Dance the grinder around, 12:00 6:00, cool surface with water soaked rag, 3:00 9:00, cool again.. repeat... it takes time, but you'll get it done and be able to pull the fitting out from the inside. Wear eye protection!! John

 

[Chuck Fort]

Update

I tried from the inside....I tried from the outside. What I finally ended up doing was cutting the old Groco seacock apart with a Dremel tool. I had to cut it up into a dozen pieces to get it off. It takes a little work to cut something that size up with a 1" cutting tool, even spinning at 35,000 RPM. Also beware of bronze dust... it gets everywhere. I had cut the seacock off 2/3 of the way around the thru-hull and it still would not let go till I started pounding on it with a hammer. then the fun part was going to get the $ 400.00 in thru-hull parts for the 4 open holes in my boat. Now it is too cold to seal them back in.