leaking thru hull on '76 Typhoon

[sloopjohnl]

My '76 Typhoon has a very slow leak at the portside thruhull that results in a leak of perhaps five gallons of water per day into the bilge at launch that slows to no leak within about three weeks. it is in a freshwater slip for six months a year. Unfortunately this model year was constructed with gate valves in place of seacocks. the thruhull protrudes thru the hull into the open space between the hull and the cabin sole liner. within this space the thruhull is surrounded by a pyramid of fiberglass that is wider at the inside of the hull and tapers down to nothing on the hull-side of the cabin sole liner. the thruhull then protrudes thru the cabin sole liner where it is secured with a locking nut. the gate valve is then attached to the end of the thruhull. there is definitely no leak at the gate valve or where the gate valve attaches to the thruhull. the leak seems to be on the hull-side of the cabin sole liner where the pyramid of fiberglass tapers down to nothing. you have to look towards the stern thru the port opening in the cabin seat/quarterberth to see the leak and is definitely inaccessible without cutting into the cabin sole liner. i cannot imagine the thruhull is cracked to cause the leak but rather is water seeping in along the thruhull where it may have delaminated from the pyramid of fibeglass? there does not appear to be any delamination of the hull where the thruhull is located. i'd love to hear others' thoughts and maybe solutions regarding this leak.

[tjr818]

Have you tried to just tighten the lock nut? Maybe the through hull is loose. It sounds to me as though, that the way to fix this would be to pull the through hull inject epoxy into any voids that you find and then re-bed the through hull. I think that the fiberglass "pyramid" has lost its bond.

[sloopjohnl]

Tim,
tried tightening the nut to an avail, but i think you are right about removing the thruhull and getting it rebonded and rebedded. that would also put replacing the gate valve in the works. thanks.

[lrak]

On my CD25 I carefully cut out the liner with an abrasive hole saw and epoxied a round block of 1" thick G10 board the inner diameter of the same hole saw. The I tapped the block and inserted bronze studs like on this page:

http://www.pbase.com/mainecruising/backing_blocks

I am much more confident in the thru hulls now.

[sloopjohnl]

That looks like a good long term solution especially for the installation of proper seacocks.

[Markst95]

Or you can go the simple way

No problems in 8 years... On a Mooring every season. Increased the hose diameter to 1 1/4". Marelon thru hulls. Drains Great!

[sloopjohnl]

Mark,
did you or do you have the fiberglass pyramids surrounding the thru hulls and what did you do or have to do to them when replacing the original thruhulls with the marelon?

[Markst95]

No pyramids on mine, just had to enlarge the thru hull holes a little as you can see in the pic. Its a 72 so this might not work the same for yours.

[sloopjohnl]

Not quite sure what the pyramids of fiberglass around the thruhull are for so i can only guess they are supposed to add some support of lateral movement of the thruhull between where it protrudes thru the hull and where the nut secures the thruhull to where it protrudes thru the cabin liner.