Has anyone seen this before

JYDPDX

2010-03-24 20:35:34

This is a picture of the though-hull for my Keel Cooler. The old backer board was rotting away along with the rib next to it so I replaced it (the backerboard) assuming I had fixed the problem. That winter I left the bonding as it was (Keel cooler not connected, somebody at some point had snipped it). Last season I connected the keel cooler to the bonding. I never thought to disconnect it for the winter. Can anybody shed some light into what's going on here? The white stuff (similar to the consistency of wet salt) in the picture was never present before and I discovered yesterday when I arrived at my boat that had been docked all winter.

tacorajim

2010-03-24 22:55:27

I've seen this before.

There's a ton of conflicting information on bonding out there. I won't argue with any of it. But, your problem is stray current from either inside the boat or in the harbor.

Either way, It's a clear example of why not to bond your keel cooler. Isolate it by removing that SS clamp and its wire. That deposit will never come back. There appears to be enough stray current to attack the fiber of the adjacent wood, over time.

Be fussy about your keel cooler zinc connections.

carojae

2010-03-26 04:03:52

I had that problem for years. I would occassionally wash it with a vinegar solution and it would clear up nicely and go away for a while. But I too got tired of fighting it as it always came back no matter how I zinc'd, bonded or whatever.

I did exactly as you did with my situation. Here's how I did it: I took the keel cooler off. I then cut a new backing block with a fresh hole - making sure it was dry and [to be] expandable when it got a little wet. I put a lot of fresh bedding compound between the hull and backing block and tightened the hell out of the locking nut when done. It hasn't leaked or did that crazy electo white display since.

The only thing I can say for sure is it is still dry. No salt water ever comes near it so I am thinking being dry is most key.

Funny, I used to attach those little trolling line zincs hoping it would sacrifice but it never did, the white powdery stuff always made it's way back.

ps-I did notice that the white stuff deteriorated the old backing block to the point of being rotten. So it is not a good thing at all.

$0.02

Jim

tacorajim

2010-03-26 16:45:36

Good point Carojae. It might be salt crystallization caused by seepage around the lock nut. But it looks like Joe used plenty of Dolphinite. So I wouldn't bet on it.

You might try sprinkling Arm & Hammer baking soda on it with your fingers. If it fizzes, it's a deposit caused by minuscule electrical current. I've had this on my truck battery posts for years. New battery 9 months ago. Same problem. Part of it will be pasty and part of it will be powdery even under the hood in summer. So it doesn't need moisture to grow.

One other thing. Sometimes folks use any old piece of wood for the backer block -- like kiln dried fir -- which in time can rot on its own in less than 10 years in a marine environment.