through hulls for the total NOVICE?!

[briangsmith]

starting from absolute scratch here on through hulls-
all 3 of mine (E25) are 28 years old and need replacing-
if only to replace the ancient, green, pitted and frozen
gate valves! (arrghh) ('plastic or bronze... plastic or
bronze'.... hmmm)

can somebody point me to the most basic, and detailed,
of threads for step-by-step how' to on this? thnx. i do have
don casey's book, 'this old boat', but find that at times he
tells me more than i need to know and makes it just a tad
bit more complicated than need be... (tho great book overall)

bgs

 

[clohman]

My boat came with Marleon (glass reinforced) fittings. One was frozen due to crustaceans inside the ball valve. Once hauled, it took two minutes to replaced the Marelon ball valve with some Teflon tape. My preference was to stay with the Marelon rather than to risk compromising the integrity of the hull by cutting out the flush mounted/embedded through hull.

I lubricate them each season with below-waterline grease and exercise them once a month. I've had no problems since.

According to Forespar, you can put a Marelon ball valve on a bronze though hull. Which through hull do you now have?

 

[NateHanson]

Personally I prefer Nigel Calder's Book for mechanical advice.

But, for here's the simplest of explanations.

First, using pipe wrenches, sawzalls, vaseline (that's for squeezing your body into unnaturally small spaces) and ingenuity, you want to unthread or otherwise remove the gate valve from the through-hull.

Next you need to unthread the backer nut from the thru hull. If the bedding compound is still strong, you might be able to just put a pipe wrench on the nut, and gently thread it off, and the compound could hold the thru hull from turning. But you probably won't be so lucky. In that case you need to fashion a tool that can be wedged into the outside of the thru hull, to keep it from turning (the inside of the thru hull has 2 "ears" inside for this purpose).

Clean off old bedding compound inside and out. Make a donut-shaped backing plate out of 3/4" marine plywood coated in epoxy. Glue this to the hull with thickened epoxy so it lies parallel to the outside of the hull. coat the flange and bottom threads of the new thru hull with sealant of choice (I like quick-setting 4200). stick it through the hole, thread on your new seacock, and tighten it down, while preventing the thru hull from turning on the outside. Clean up excess sealant.

Drill into the backer block (not too far!) and use 1" bronze lag screws to attach the seacock mechanically to the backer block/hull.

 

[Emerald]

Hi,

You mention sometimes wanting the simplified nitty gritty so to speak, so here's a page I put together on thru-hulls:

http://home.comcast.net/~ericson-yachts/thull/thull.html

There are a lot of slight variations on the theme, but this should get you in the right direction.

Some more thoughts. Don't get lulled into thinking the bronze on the boat is in good shape. Replace it all. I say this from the experience of having replaced everything but the actual thru-hull (this was on a '66 Columbia 24 I had years back), and went to wiggle a new drain line on the new barb on the new ball valve, and the whole thing broke off between the ball valve and the hull. I was supposed to launch the next morning, and was very happy I didn't save hooking up the sink drain line until after launch.

This brings up something else. Thru-hull fittings and seacocks are straight thread, but ball valves are NPT - a tapered thread. Beyond not providing a solid valve to hull joint like a seacock threaded down on to the backing pad, they don't thread properly.

I like using a good quality pipe dope instead of teflon tape on the threads. Coat both sides of the backing pads as well as the thru-hull with your adhesive/sealant. For bronze, I've had good luck with 5200 Fast Cure. For plastic, I use the 4200 Fast Cure. When you tighten down, hold the thru-hull and turn the seacock. If you spin the thru-hull, you'll spin out too much sealant. The old timers who guided me on my first thru-hulls prefered to tighten up nice and snug and leaving alone. Many others like a technique of partial tightening, then waiting for the product to cure, and then final tightening - the idea you leave more material being squished as a gasket. I've always done a nice and snug torque with large wrenches and left them alone, and have not had any issues.

While you are at it, check out things like your knotmeter sending unit. I had a core disintigrate on me when I pulled it out of the housing - it was being held together by the compression of being in the thru-hull fitting. Pretty scarry to think I sailed a season like that.


Good luck, and keep us posted.


-David
Independence 31
Emerald

 

[rwthomas1]

My recent seacock/thru-hull replacement was quite the experience. First thing I noticed is the original plastic thru-hulls cracked fairly easily in trying to remove them. Dunno if they were "marelon" or not but they were 20+years old. My guess is plastic degrades like anything else over time. Beware the old plastic units.

Secondly the thru-hull nuts were easy to remove but the thru-hulls themselves were attached very well with whatever they used to install them. Twisting, pulling and beating them out with a mallet was required.

Thirdly there was absolutely no way to turn the seacock to tighten them instead of turning the thru-hull from the outside. On my E38 the seacocks were close to each other and hull structure and this was impossible. The way to do it is to bed the seacock, drop it into position and then thread the thru-hull into it. The sealing surface of the thru-hull only makes contact during the last few revolutions of the tightening process. Yes the sealant "turns out" a bit but if you use a lot, and I mean plenty of excess sealant then this is no big deal. Put pipe dope on the upper thru-hull threads as you don't want water chasing down the threads and into the backing block area.

I prefer 4200 or something like polysulfide for seacocks/thru-hulls. They may need to be removed in the future and 5200 will make this very difficult. I don't buy the partial tightening method. This will only break the adhesion seal of the sealant by moving the parts again. Torque it down and wipe up the excess sealant.

RT