Tightening of thru hulls, seacocks, and fittings

[Chum Bucket]

Boat is a '79 33SF. I'm hauling out next month or so. I will be changing out ALL below waterline plumbing, thru hulls, and seacocks. I've had water in the bilge since buying the boat so finding the source of intrusion has been impossible. Now is the time to eliminate all NPT to NPS junctions and soggy wood backing plates. Since none of it is original and integrity is suspect, I would feel much more confident 50 nm offshore knowing what's below deck. I'm installing Groco SCC1500 safety seacock conversions on the engine intakes, but not my first preference. I wanted to do another set of inline seacocks off of a tee fitting, but I will not have the room without sacrificing access to my Racors and STB raw water pump. Starting from scratch and will try to do it right the first time! I'm using bronze, flanged seacocks and 1" fiberglass backing pads. I will be following the advice of the marinehowto.com guy's suggestions. There are 7 to contend with. I have only had to change out ONE thru hull in my life, so I lack much hands on experience.

With regards to assembly, just how tight should the fittings be? I'm a big guy so with the right tool and cheater bar, I can do some serious damage! I bought a pair of used 1-1/4" Perko strainers ($100) with some pipe and fittings attached. BTW, Perko replacement parts cost an arm and testicle. good gawd! The attached plumbing was wrenched on extremely tight, but there was substantial surface corrosion too. None the threads were damaged during removal, but it was a huge PITA! Using the strainers as a gauge, is that the norm?

Obviously the taper threads have a limit of how many turns and NPS will bottom out. Guess I'm looking at some guidance about how far to go after my hands can't turn the fitting? I've read that quality pipe dope and Teflon tape is a must. It would sure be convenient to finally have a reasonably dry bilge for a change!

Any wise words from the faithful?

[neil]

Don't forget to check your transducer,ask me how I know,almost sunk the boat at the dock this summer.we had checked everything after we noticed a lot of water in the bilge if we had gone offshore it would have been a nightmare at sea

[Yannis]

I removed my through hulls last week and the leaking flange in between.
I ll put them back without a flange of any sort, just some Sikaflex. I believe this silicone like white paste has a name in the US, that I'm unfamiliar with.
Also, look into Nigel Calder's book for the plastic (marelon) through hulls that are oblivious to electrolysis.

As to the through hull/seacock connection, I would not use teflon tape in any way, rather, I'd apply this liquid metal glue that sets quickly. Screw finger tight and then give it a half turn with the spanner. To undo (when time comes), heat up and unscrew. I have done all my freshwater connections with this glue(where applicable) with no issues.
Good luck.

[Chum Bucket]

Thanks Gents.

Last haulout, I installed a new transducer and is THE only thru hull I know is not the culprit. I suspect all the backer boards are waterlogged/rotting away and the seals are compromised. I am sure my monthly opening and closing of the seacocks puts additional stresses on the seal. Fiberglass backers epoxied to the hull and flanges should eliminate that problem...forever! The previous owners did not exactly take the time to do things correctly. Like I loved the household twist nuts on some of the hidden wiring. The surveyor and I were laughing! I'm sure the plumbing is no different.

Yannis, liquid metal glue? Is there a particular brand you use? I'm hoping I'll never have to do this project again, but as we all know, nothing is forever on a boat! Def need to be able to take apart.

Once the project gets started, I'll post some pics. I'm sure there are other Berts that need updated thru hull/seacock work here.

[Tony Meola]

Kevin

A couple of things, you don;t want to tighten them so much that you crush the glass. It can be done. You want them tight but as my father used to say, don't screw the eyeballs out of them.

I used fiberglass plate on ours as backing plates. They were glassed to the hull with thickened resin then we ran glass mat over them. Maybe overkill but it works.

I just get them tight and if they are bedded right they will not leak. What ever you do, Do not and I repeat, DO NOT USE 5200 TO INSTALL THE THROUGH HULL. If you ever have to remove the through hull you curse yourself out if you use 5200.

Also what ever you do, don't tighten the through hull out of the box. Get your sealant on the flange on the outside of the hull, and tighten it until the sealant starts to push out. Let it set up overnight then tighten them up. This creates a gasket of sorts.

The great debate on installing through hulls is if the threads need sealant or not. I never use any type of thread sealant. They are designed to thread so they do not drip or weep. If you put on too much sealant, you will interrupt the bonding of metals. Remember all thru hulls should be bonded into the grounding system. You should have a bonding strap running around the boat.

By the way, this is a two person job. One to hold the thru hull to keep it from spinning and the other of course to tighten it up.

Good Luck.

[Yannis]

Kevin,

I'll ask about the liquid metal glue and revert.

I do not understand what the reason is to put any sort of flange inside the hull when installing thulls. For me, an additional item is an additional source of problems. And this very flange of mine was the source of my leaking.
Unless the boat bottom is weak, which is not the case in my 28 as it is also not the case in the 31 (there is a good 2+ cm thickness in that area) and if there is no problem with the angle inside the boat, then why add a flange/wedge ? For strength? Not needed. For added sealing capacity? Not true. Beats me.

By the way, has anyone used that little hole on the outside of the thull to screw it in place so it doesn't twist when you tighten it from the inside? How clever is it to add screws on the hull? Thanks.

[Chum Bucket]

I haven't used 5200 in a few years. Experience has taught me that there is nothing on a boat needs 5200, absolutely nothing!