How to remove through hull valve

J

jkswor

New member
Cd Dory 07 25 ft cruiser. Have a through hull valve under step by door. Seems to be letting water bypass it and leak into area. Going under spray on fiberglass top layer by a stress crack. That make sense? Any how has to be coming from the valve seal. This is used for the deck wash down pump
Any one know how to remove the through hull valve unit? So I can see if that’s the problem and if so repair it
 
The boat has to be out of the water to remove the thruhull fitting. There should be a large nut around the body of the thru hull fitting. That has to be loosened. The fitting which is right angle, and the valve have to be removed. Then unthread the thru hull, out of the bottom of the boat. You can keep the thru hull fitting by putting a serial plate in the outside of the thru hull. there should be slots for a properly sized "plate" so it can be fixed and not rotate. This is a 2 person job. If 5200 was used as the sealant, it may take some debund and or heat to loosen up the sealant of the thru hull to the bottom of the boat.

Now you have the valve, the adaptor to the thread size, and the elbow out..You can examine the inner fiberglass. Hopefully there is no rot in the core. You will have to take a small Dremel bit or even a bent coat hanger 2" piece to cut any core within about 1/4 inch from the hole opening. You should have dry core. It is wet, then it has to be removed, down to dry core. After you are back to dry core which has been removed, you will fill this void with epoxy resin thickened with cabosil and medium density filler. That goes off, the edges around the hole are smoothed up with a drum sander checked in a drill. Then you are ready to put the repaired thru hull fitting back in the boat. If there is any glass defect on the inner side, this is the time to grind it out and rebuild any top surface which was damaged. 1708 cloth laminated with epoxy resin makes the best repair.
 
My washdown pump uses a through-hull fitting like this with the valve screwed to the top:
https://www.westmarine.com/groco-3-4inc ... f6EALw_wcB


If yours is similar, your steps would be to disconnect the hose from the valve, remove the valve from the through-hull stem, remove the nut that holds the through-hull to the hull, remove the screws underneath, then remove the through-hull.

A top-quality marine penetrating oil often helps remove the threaded connections. Spray the exposed ends of the threads, tap with a hammer to break corrosion and let it seep in, then wait 24 hours. The difficult part may be the sealant used to bed the through-hull fitting and nut. 5200 sealant is commonly used for through-hull fittings, and it can be very difficult to release. You can soften it up by heating the metal fittings with a hot-air gun or propane torch. Obviously, use heat with extreme caution to avoid scortching the fiberglass.

If your through-hull ends with a mushroom underneath, it may be helpful to buy a through-hull installation wrench. Here is how that works:
https://www.youtube.com/watch?v=W5pL96HI9FQ

Good luck!
 
There are special tools you can insert into the outside of the thru hull. Some have little tabs into the bore of the thru, some have slits cut into the lower part of the thru hull. The former are what "Mutski" links to.

I cut and shape a steel piece to fit in the lumen of the thru hull, and hold that in with a pair of vise grips locked on this small steel plate. It can fit into the grooves, or impinge against the tabs (if you don't want to shell out the $60 for the special wrench, or it has the cuts rather than the tabs.

You don't really unscrew the outer part, the entire threaded part of the thru hull should just slip out (after any bond from the sealant (hopefully not 5200. There then several steps to putting it back in--after you have repaired the thru hull hole, as I described above.

There are videos on the internet.
 
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