Wood Base Plate Rot

[Hudson Force]

I have some through-hulls without true seacocks, but simple stainless ball valves set in bronze for a couple of sink drains as well as a spare unused through-hull in my engine room. These are set on wood plates from their original installation and approximately twenty years old.

I was lubricating and exercising all my seacocks and ball valves today and noticed that my one spare unused ball valve in my engine room had an area of dry rot on a top corner of the wood disk.

By my bottom condition, I'm not planning to hull out for two years. The current amount of rot is not encroaching upon the area of the metal through-hull but I want to stop it's advance. This one with the rot was treated differently as I had covered the wood with a thick white paint when my engine room was empty for repowering and fuel tank replacements.

So,.. a biocide ..... a nonviscous impregnating expoxy ..... entomb it .... let it aerate .......? What's my best strategy to buy some more time?

[Schooner Chandlery]

All our through hull fittings are extra long threads and mounted on over2" thick white oak or purple heart blocks. Our boat is wood as well. Paint can hold moisture under its surface promoting rot by the way. Our blocks are about half and half painted vs natural finish with a sealer.

If your backing block is composite or plywood it may rot quickly without a proper sealant.

You could remove paint and then apply a penetrating sealant that will displace water. Then repaint. Choices of sealants include smiths clear penetrating epoxy sealant 'CPES' as well as the Wolner Woodlife Classic which happens to be water based and water cleanup.

The sorts of things that folks wary of rot place on various parts of wood boats include a wide range of products. You can use a red lead primer or white lead paste mixed into a paint as lead seems to stave off some aspects of rot. Others use mildewcides and additives to paints. Some folks swear by a soak in ethylene glycol (yes antifreeze) and some people will use a coating of bees wax for its water resistance and natural antimicrobal properties. Finally there's a trick of using Stockholm pine tar dissolved in a bit of turpentine (and a touch of Japan dryer to make it cure) to preserve suspect wood.

If you don't have a wood boat you probably shouldn't have wood backing blocks JMO.

If it were my boat I would use what I have handy-short term that is. So if the wood isn't too punky I would want to soak it with many coats of CPES or Woodlife and then paint it with red lead primer or white lead paste mixed into another paint. I have all these materials at hand.

If you don't have any of the materials I mentioned, I dunno, because often using what's readily available is the best fix.

Good luck.


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[Hudson Force]

I'm not underway or moving about soon. I'm docked in a good size city. I have everything available. I like the penetrating epoxy plan, but I could treat with a biocide or ethylene glycol first.

While were at it,- what about an alternate back up plate,- composite? Should I care?

I was buying light bulbs today and judging between the 9 year bulb and the eleven year bulb for a slightly higher cost. 'not a choice that I'm going to be concerned with!

[Schooner Chandlery]

You probably won't do any change out until your next haul out. Being a wood boat person, I can't really advise regarding the right backing material for a fiberglass hull. I just don't think wood is it. 😏


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[mitiempo]

Originally Posted by Schooner Chandlery

You probably won't do any change out until your next haul out. Being a wood boat person, I can't really advise regarding the right backing material for a fiberglass hull. I just don't think wood is it. 😏

G10 is the best choice for a backing material on fiberglass boats. Fiberglass is a good second choice. In both cases epoxied to the hull.

Some links to help:

Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine How To at pbase.com

Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine How To at pbase.com

Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine How To at pbase.com

[Jim Cate]

IMO, Hudson, a timber backer well treated with epoxy is quite acceptable in your hull. The epoxy will keep water out, and that keeps rot away. It is not a structure that is exposed to much stress, after all. G-10 or glass laid up with polyester to an appropriate thickness would be good, but not necessary.

Jim

[thinwater]

Why are we defending wood? $2 worth of GRP would have been forever. Silly.

[UNCIVILIZED]

There are various ways to fit new ones without hauling out, if such is off interest. Albeit, generally they're not quite as neat & clean a fit, as if fitted in the standard manner. Nor, necessarily are they meant to be permanent.
Though much of the quality of fit & installation depends upon how you put them in. So if it's truly rotten...

[RaymondR]

I use disks cut from 1/2" - 3/4" poly cutting board for a lot of this stuff these days, cheap, easy to find, does not corrode or rot, has a little give which helps both preloading and over tightening?

[UNCIVILIZED]

Originally Posted by RaymondR

I use disks cut from 1/2" - 3/4" poly cutting board for a lot of this stuff these days, cheap, easy to find, does not corrode or rot, has a little give which helps both preloading and over tightening?

Hate to have to tell you this, since it sounds as if you already have some of this material installed. But it has very little strength, & doesn't belong in such a critical application.
I've seen it crack, & or split, under any kind of significant loading. Especially point or shock loads. And the properties of this material were covered in depth in a recent thread.

[Hudson Force]

I will treat this one back up plate with something, likely an epoxy, in order to keep it in satisfactory condition until my next haul out. It's important to note that this one plate was mistreated by me when I entombed it 15 years ago.

The eight other identical wood plates that were installed over twenty years ago are in excellent condition and look like they will remain so beyond my lifetime. I can't fault the wood.

I'll likely be more attentive to the condition of the bronze fittings when selecting replacement than the wood plates; however, any through haul that needs attention will be fully replaced.

Thanks for all the ideas.

[HopCar]

Hudson, I think you've got the right plan. Treat it now with penetrating epoxy like Git Rot and keep an eye on it until you can replace it. Groco sells ready made fiberglass backing blocks that are pre drilled to fit their seacocks, their flanged adapters and Apollo seacocks.
Groco Seacock Backing Block