Leak source found - fix?

[quailrunner]

New question from an earlier post. I have found the source of the leak in my boat (thanks TexasA&M and Loneranger for help); the depth finder thru-hull transponder is leaking. What do I do about it? It looks fairly easy to unscrew it inside the boat and push the unit out through the hull; should I get a new one or just reseal it? And is there a specific set of issues in resealing it?

Any advice appreciated!

 

[Dave S]

Typically, the transponder is in two pieces, the mounting itself and the transponder unit which fits in the mounting. It is probably similar to this.

The transponder itself can be removed easily by unscrewing the collar on the top of the mounting and pulling it out (with the boat out of the water of course:smt043). There are o-rings which seal the transponder in the mounting. But are you sure this is where it is leaking or is it leaking around the mounting itself? If it is the latter then the mounting will also have to be removed and re-sealed.

Dave

 

[quailrunner]

Dave - thanks for the detailed reply. My unit looks almost exactly like your photo. I do not know the answer - I have the boat out and on the trailer, so I can pull the unit and then test to see if its the unit or the mounting w. food dye and water or some such approach (red Koolaid worked pretty well in determining that it was the depth sensor that was the general location of the leak; it leaked out when I raised the boat up in the lift). I'll look at that this coming weekend. If its the mount, do I need to worry about water getting into the hull in that area? I don't know if there's wood in the bottom of a 2006 Sea Ray 185 hull or not.

Thanks again!

 

[springer3]

No affiliation, but 3M makes a marine adhesive/sealant for applications below the water line.

Bath tub caulk will do the trick for a while, but will not last.

Let us know if there is wood in the bottom hull. I hope not, but most panels on my 215 EC have plywood laminated in the fiberglass. Rot is a real concern if water gets in behind the fiberglass.

Good luck fixing the leak.

 

[quailrunner]

Thanks! I'll know this weekend if there's a plywood issue.

 

[quailrunner]

Interesting - I'm not the original owner; I suspect that means I cannot apply for this coverage?

Anyway, I fixed it yesterday. It was easy enough to loosen the lock nut and pop the transponder through the hull. The silicone in between the transponder and the hull (there was no thru-hull, just the transponder itself) was not heavily applied. I have one definitive answer: There is no plywood in the 2006 185 sport hull, at least not in the bottom. Its 5/8-3/4" straight fiberglass. I cleaned the transponder and the hull well, and then hung the transponder down about 1.5" below the hull, and covered it with a lot of silicone. My son turned the locknut while i held it in place after slowly working it up into the hole. I tested the repair yesterday - no leaking at 40 mph or tied off at the dock for 3 hours.

The leak clearly developed from inside, due to dirt (I could see a channel in the silicone). The transponder was mounted at a point where the hull (inside) is *not* flat, but changes from a little platform that the bilge pump is mounted on to a slightly lower level (I can post a photo tomorrow). So, the locknut is not drawing up evenly; the stern portion is squeezed tighter than the bow portion, and it shows in a slightly (1 mm) skew (bow, not stern) under the hull. This is clearly what caused the problem in the first place, and I think it will happen again.

Question: Can I deal with this by expoxying a faring block to the hull (inside) to provide a flat surface for the locknut? Are faring blocks sandable so that I can make one fit on the (not-flat) existing surface?