Scupper through-hull seepage repair?

[steve poulin]

So during the last week of the season I discovered about a half inch of water in the drip pan beneath the engine. The bilge, despite heavy late season rains was bone-dry.
I have traced the seepage back to the port side scupper through-hull (please see photos), and project that this will be my first major off-season repair (I am on the hard as of today).
I imagine several of you esteemed CD owners have tackled a similar project—what have you learned? What am I in for?
Thanks for any/all advice
Steve

[sloopjohnl]

just did the thru hulls for the two cockpit scuppers this season on my 76 typhoon. the adhesive sealant on the exterior of the hull where the thru hull passes thru the hull was degraded and no longer sealing out the water. disassembly is the hardest part. as Cape Dory originally used gate valves attached directly to the thru hulls and i wanted to get rid of the gate valves, i simply removed the thru hull by cutting below the gate valve with a sawzall. the thru hull practically dropped out thru the hull as the sealant was so degraded. i replaced everything with new from Jamestown distributors and sealed with SikaFlex 291. Good Old Boat magazine recently had a thorough article on this procedure and i believe MaineSail has a good tutorial on his website.

[JD-MDR]

Search thru hull replacement or service, There are excellent threads on the forum. I'm an amateur but it looks like the seals failed at the hull. The expensive Spartan tapered cone thru hulls might be OK.
A couple of mine are horribly pitted . I lapped them and greased them and they are working fine. Though I rarely use these ones to the head. I keep them closed. I will replace someday.

[jbenagh]

Check out this thread:
http://capedory.org/board/viewtopic.php?f=9&t=33755

I bet the thru-hull is fine. You can clean it up while it's out. Also, replace the backing plates with 1/2in G10 since they are probably close to failing.

Jeff

[sgbernd]

This is not so big of a job, nor expensive, but is time consuming and messy. You need to re-bed the thru-hull and your backing plate is probably in need of replacement. The key is to clean up everything perfectly (both the hole and the thru-hull and the threads) so that the new sealant can properly seal. I used a very small screw driver on the threads to remove all the old calk, dental pick, etc. then washed/soaked the bronze bits in hydrochloric acid to remove the corrosion. Replace the nuts, bolts, and grounding lug. Grind the tapered plug with lapping compound until it is smooth and shiny at the seals, clean, grease, and test it by letting it sit overnight filled with water on a paper towel or plate to check for drips or dampness. No water should escape either thru the sides or out the bottom.

Scrape/dig/sand the holes in the hull (both the thru-hull and the screw holes) until you are confident all the old sealant is gone and only clean fiber glass remains. Probably the failed sealant is silicone, and if any remains in the hole, the new calk will leak. Wipe everything with a good solvent (Acetone, etc.) and make sure it is clean, dry, and has shows no residue. I didn't need new backing plates but yours looks like you do so that is another layer to work thru.

To reassemble, it is a two man job, one to insert the thru-hull from the outside and thread it into the sea cock, and hold the screw heads while the man inside tightens the nuts.

While you are at it, check all the other thru-hulls. It isn't much harder to do several of them than only 1 and you won't need to deal with it for another decade or two.

-sgb

[steve poulin]

Great advice, thanks everybody. Jamestown has pre-cut 1/4 inch G-10 backing plates. Are these too thin to replace the existing plywood backing plate? Too weak? I don't have a drill press and it sounds like working with the 1/2 inch G-10 will be my biggest challenge. Also, I have some 3M 5200 from a dinghy repair--will this work as well as epoxy for attaching the backing plate?

[JD-MDR]

I don't have any problem cutting or drilling thru 1/2 " g-10. I cut with my disc grinder and the diamond blade. I bet the metal cutting blade would work. I got the feeling nobody likes 5200 any more. I use 4200, above the waterllne at least . I haven't transitioned over to butyl stuff yet. Oh, all the comments I see are for using 1/2 " backing plates. I like to comment just to hear any critiques or corrections. Lets see what they say.

[steve poulin]

Is the purpose of the step wrench, improvised or otherwise, simply to support the thru-hull as the seacock is unscrewed? To remove torque from the thru-bolts and keep those holes from cracking?

[sloopjohnl]

for boat thru-hulls that is pretty much the story. and if you need to buy one Home Depot has them for $15 as compared to marine outlets that ask $65+.

[sgbernd]

If you don't feel like purchasing a step wrench, I used a regular Craftsman wrench, the kind that is open on one side and closed on the other and come in 1mm or 1/16" increments. Take your whole set, and find the size that will insert snugly into the thru-hull sideways and large enough to catch on the two bars on the inside of the thru-hull. Then use a big Crescent wrench or whatever to apply leverage to the wrench and unscrew the thru-hull. It is rather abusive to the wrench but they are pretty strong. You are only breaking the calk so the torque is not so high.

If you already purchased the step wrench, you may need to mill out the channels because the Spartan thru-hulls have rather thick bars and the standard step wrench (at least the one I purchased) had grooves which were too narrow to fit (and also explains why the previous solution was devised). I have since milled out the step wrench for the next time I need it and will see if it works.

-sgb