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post #1 of 15 Old 05-03-2012 Thread Starter
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Leaking transducer through hulls

The speed and depth sensors leak for a few weeks at the beginning of the season until the fiberglass swells and it stops up. It wasn't something I noticed when we bought the boat as it was in the water, but the PO had wrapped paper towel around the sensors to sop some of this up until it self sealed. This doesn't seem right. So, two questions.

1) Is it REALLY terrible for the glass around those ... i.e. how much water penetration. If it's really bad, then I absolutely need to deal with it before I put it in the water, but...

2) Is the fix easily undoable. I want to replace my instruments in the next year or two, but hadn't budgeted for it this year. I'd hate to use 5200 to seal it up or something and then have no chance of getting them out next year.

1978 Morgan OI 30
Au Gres, MI
Lake Huron
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post #2 of 15 Old 05-03-2012
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Re: Leaking transducer through hulls

Fiberglass absorbs maximum 3-3.5% water. But this might cause osmosis. It is best to apply a few coats of epoxy to the holes. Tightening the thru hulls after this operation should stop water ingress. you can use 5200 (poliurethane) before attaching the the thru hulls. Polysulfide is less stickier than poliurethane.
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post #3 of 15 Old 05-03-2012
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Re: Leaking transducer through hulls

Are you sure there isn't some wood involved? It definitely swells. I only ask because this was the case with our transducer that leaked for a couple of days after splash. As I remember it, I found a square of (rotting) plywood bonded to the inner hull, and the transducer clamped to the plywood. I removed the plywood and 5200'ed a piece of fiberglas sheet (from McMaster-Carr) in its place for the fix.

Tom K

2000 Beneteau 331
Northern Chesapeake Bay

Ambition is a poor excuse for not having enough sense to be lazy ~ Steven Wright
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post #4 of 15 Old 05-03-2012 Thread Starter
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Re: Leaking transducer through hulls

I guess I'll find out this weekend. I'm heading out to remove shrink wrap and start on a list of projects. I think this is more of a scouting mission than anything

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post #5 of 15 Old 05-03-2012
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Re: Leaking transducer through hulls

Pull the 'ducers and rebed them properly before you splash -- the peace of mind alone will far exceed the work involved.

Pay close attention to any backer blocks you remove as you disassemble. Depending on your hull shape, your depth 'ducer should be on a beveled block that orients it vertically and not necessarily perpendicular to the hull. If the blocks are made out of plywood -- and many are -- make sure that they are sealed; if they aren't, inspect them very carefully for any indications of delamination or rot. If they show any signs of damage, make new ones and seal them with a couple of coats of epoxy.

I'd be very hesitant using 5200 for anything here -- it's just too permanent.
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Re: Leaking transducer through hulls

Thanks guys. I'll take a look for the backing block. I suspect you may be right that it needs to be replaced and the transducer rebedded. I strongly suspect I won't be eager to replace anything for a few more years, just as well, maybe instruments will come down in price a bit more :P

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Lake Huron
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Re: Leaking transducer through hulls

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Originally Posted by rhsanborn View Post
Thanks guys. I'll take a look for the backing block. I suspect you may be right that it needs to be replaced and the transducer rebedded. I strongly suspect I won't be eager to replace anything for a few more years, just as well, maybe instruments will come down in price a bit more :P
This shouldn't cost you much at all (other than time that is.)

Plywood backing blocks are perfectly acceptable (as long as they're sealed) and you can make these yourself. Drilling the hole for the depth 'ducer to the proper angle would be a snap on a drill press, but can also be done freehand as long as you're careful. Your tolerances are not critical (i.e., a gap of 1/16 should be fine), since the sealant will fill that gap easily.

So, you're looking at time invested, a tube of sealant, some scrap plywood and a little epoxy -- should come in at under $25... Waiting and being forced to haul the boat once your current leak becomes unmanageable? Hundreds... Pretty clear math for me
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Re: Leaking transducer through hulls

Pretty clear math indeed. I'll be rebedding and rewiring all the instruments though. I just don't want to do it again for a while. Definitely worth doing. I'm slowly undoing some of the silly work arounds from the PO... one at a time.

1978 Morgan OI 30
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Re: Leaking transducer through hulls

This is nothing, ball valve seacocks, that probably need to be rebedded as well, and then the sanity system ... yuck.

1978 Morgan OI 30
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Lake Huron
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post #10 of 15 Old 05-03-2012
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Re: Leaking transducer through hulls

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Originally Posted by rhsanborn View Post
I'm slowly undoing some of the silly work arounds from the PO... one at a time.
And that, my friend, is the true definition of boat ownership.
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