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Re: Raymarine ST40 speed transducer nearly sunk me
I used 4200 to bed the thru-hull and that's not what is leaking. The blank plug leaks too.
I think what happened is this: the hole for the thru-hull is located under the bow, right in the middle where the hull forms a vee. The thru-hull fitting is plastic, instructions say "hand tighten only". I think I overtightened. "Hand tighten" used to mean "tighten as hard as you can with your hands" lol, now I know better. I think the instructions should say "snug", anyway... When that plastic thru-hull was tightened too far it deformed because it's not on a flat part of the hull. The two o-rings on the transducer (and plug) no longer formed a water tight seal. That's my theory.
I happened to have a spare o-ring for the fuel fill, just so happened that it was the exact same size only slightly thicker. I replaced the top o-ring with that and it slowed the leak further. Hmm... I went out and got another o-ring to replace the lower o-ring but couldn't find a suitable size. I ended up using the yellow plumbers tape simply because it's what I had, to build up a layer underneath the original o-ring. It worked. Leak is now stopped.
That doesn't mean I'm not hauling the boat in the next few weeks to replace the thru-hull with raymarine's bronze version.
4200 is fine. You don't need to "glue" the thru-hull into place. The mechanical hold is supplied by the threads etc. All you need is something that'll keep the water out. C&C used butyl tape down there, never once leaked as evidenced by the bare plywood backing plate, bone dry. I used 4200 on the rest of my thru-hulls and they are fine too.
Last edited by smp; 05-06-2013 at 11:00 PM.