Leaky Stanchion Base Repair

[shellphish]

I've noticed that the backing plate for a stanchion was looking really rusty and the shelf underneath it was looking a bit warped. I put the issue on my list but deemed it 'ok for now' since this winter has been really dry. Well after leaving my laptop near the leak, spraying the deck and subsequently soaking my laptop the issue has moved up the list.

I've read that re-installing the stanchion with strategically placed silicone will fix the issue but I'm assuming that the rusty backing plate should be replaced as well. The backing plate looks original and the cabin interior coating goes over it. Will it be a problem if I took a chisel to the plate and replaced it with an aluminum one (also a something I've seen suggested) and re-seated the stanchion with silicone 'seal'? Also what exactly is the stuff used to paint the cabin? Special sealant or just paint.

[JPA Cate]

Try scrubbing the backing plate with steel wool (on the dock, not the boat, to avoid rust stains). If it cleans up easily, it was stainless and you've had the leak for a long time. (Sorry about your laptop). Better you should use "Life Caulk" or 3M 4200 for the sealant.
The problem with using silicone seal is that it is very difficult to remove completely and it will be difficult to get anything to adhere there again.

Ann

[ravinracin]

I am in the process of resealing all my deck hardware and installing backing plates. For the stanchions, I remove the bolts. coat the hole thru the deck with epoxy, wrap the top of the bolt threads with butyl, and put a ring around the base of the stanchion where it meets the deck, put it all back together and am done. It should not leak. Also my boat deck hardware did not have backing plates, just washers in the inside. I am using aluminum backing plates.

[heron237]

Whats wrong with marine silicon as the sealant? So long as you do it right. Let the silicon get 90 percent cured before you tighten your bolts. Butyl is another good choice if you counter sink your deck holes first. There are threads on here that go into great detail as to how to properly use butyl tape. Don't use steel wool, scotch bright is the way to go.

[Hudson Force]

The first thing that I would identify is wether the stanchion bolts are passing through a cored section or solid epoxy. If the location of the base plate is cored, then there is the possibility that the source of the water is at another location. If the bolts of the base plate are passing through a sound solid epoxy area, then the only need is to seal the possible access of water down the fasteners. I would agree with AnnCate's suggestion to use the 3M4200 or the polysulfide, but also not the silicone. I personally like to use the 3M5200 that so many curse due to it's difficult removal. This very difficulty in separating it from it's cohered surfaces is what I value. I can always get it separated with a fillet knife or a guitar string. I usually don't concern myself with filling the threads or passage with the sealant, but I run a bead in a circle around the fastener's hole with enough volume that it will press against and full around the bolt. I'm all for cleaning the back-up plate, but don't seal the exit for the leak. Only seal the potential entrances for the leak. There's no good in attempting to trap water above your back-up plate. I also follow heron237's wise advice about comming back the next day for tightening the work. It's not a good idea to press out all your sealant with a tight fastening before it's had some curing time. Back to the first concern. If you do have a cored area that the fasteners pass through, the best solution is to remove the core at this area and fully expoxy the bedding location.

[delmarrey]

The syndrome of leaky stanchions is the deck thickness where the bolts pass thru.

If you can wiggle the stanchion when fully tight, it will NEVER seal completely.

What I've done is epoxy 1/2" G10, twice the size of the backing plate, to the underside and drill thru, then add longer bolts.

This gives it more strength so it doesn't wiggle and add more hole length to seal the bolts.

And if you going thru core material you're going to need to dry it out and epoxy plug the holes as well.

[roverhi]

Sillycone belongs in boobs not boats. Sillycone is very hard to clean up, solvents don't effect it and it leaves a film unless you spend a bunch of time scraping up the crap. It leaches into the gelcoat and if you ever want to paint the area in the future, will have to sand through the sillycone contaminated gel coat. Worst part is it doesn't seal all that well. Have spent countless hours rebedding leaking fasteners that were originally done with sillycone.

I'd use Butyl for sealing stanchions. Because they get badly torqued with people using them to climb aboard, push the boat off, or just being stanchions, you need a caulk that's very elastic and will take the movement. LifeCaulk and 4200 are good caulks but don't have the elasticity of Butyl.

If you were going to paint the deck, you could make pads like Delmarrey says only put them under the base of the stanchion, Makes a neat looking addition will spread the load better over cored sections, if any.

Don't use steel wool on any stainless. The steel wool or any ferrous metal, wire brushes, etc. leave pieces of itself imbedded in the SS and turns into an ugly rusty mess. Use Scotch Brite to clean up the backing plate. Assume it's SS but if it's plain steel replace with either aluminum or fiberglass backing plates with fender washers.

[HansSolo]

I second butyl. Heres a good writeup explaining how to best use it as well as a good source to buy it Re-Bedding Deck Hardware With Bed-It Butyl Tape Photo Gallery by Compass Marine at pbase.com
What ever you do, stay well away from silicon or 5200. Both have very limited uses on a boat in my opinion.

[Hudson Force]

Originally Posted by delmarrey

................
What I've done is epoxy 1/2" G10, twice the size of the backing plate, to the underside and drill thru, then add longer bolts. ..............

Excellent advise!

[shellphish]

Sorry folks I work too much and don't have access to a computer as much as I wish so I'm not quick to reply.

There seems to be a divide in this forum like most other places I've searched over silicone vs 5200 and 4200, roverhi made a good argument for Butyl since the stanchions do flex quite a bit, the sealant used should be able to cope with it or it will fail quickly. The way it is now there is plenty of silicone slathered over the base and clearly its not doing the job. In other news, one of the stanchions that has been reseated by PO and I saw duct tape sealing the backing plate for it in the cabin . Hopefully I'll have time to re-seat the leaking one and check what nightmare is awaiting me under the duct tape on the other one over the weekend. Thanks for all of your input!