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Old exhaust through-hull replacement


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Previous owner of the new to me, but not to the world, boat with a Yanmar diesel said he wasn’t sure how water was getting in when the cockpit was fullly loaded. 

I have a guess (see attached photos) and I bet you do too. 

This through-hull looks quite old (bronze?). 

My first question is - will it be fused together? (And if it is, how the heck am I getting it out?)

My second is - if I can get it apart, can I reasonably clean it and reuse it, or should I get a new one? 

New exhaust through-hulls seem to be made to screw into the glass. That seems odd to me; I would want it to bolt through to something on the inside for strength. Is there a better replacement? What would you use? 

Finally, what should this be bedded with when I do replace it? 

Thanks for your advice! 

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5D2C649A-D7A5-48CE-AA58-D172F24DC9C7.jpeg

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3 hours ago, sierrawhiskeygolf said:

It looks like bronze and although it looks crusty, you should be able break the nut free, bronze won't normally seize.

Thank you! I didn’t want to try in case I broke it off without a plan, but that’s reassuring! 

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I'd worry a little more about the plastic ones. They tend to get brittle in the sun and eventually break, and those seem pretty close to the waterline. 

The best permanent fix for something like those is to remove them, and bond in a hard fiberglass tube. A certain amount of work, but you only have to do it once. 

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It looks like the bronze one has loosened and should be re-bedded. You might be able to get a locknut for it. 

Replace all hose clamps while you’re at it.

Does Marelon hold up better than the cheaper plastic?

What sources for fiberglass tube?  G10 or something else. 

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Marelon holds up great. I just replaced a 38 yr old RC Marine one because the valve seized. Next time I'll just thread on a new valve - the through hull was near indestructible and not at all brittle even after all that time.

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@DDW They are close to the waterline - thank you, I will look into the health and potential replacement for those. 

@Diamond Jim I will look for a locknut, and I’m going to replace all the clamps on the hoses - a couple of them look like 316 bands with some other steel for the bolts and they’re rusting out. 

Thanks all, this is great info - exactly the kind of perspective I was hoping for. I’ll also look at the flexibility of that tube to make sure it’s still good, and look at the other two through-hulls. I’ve been a longtime lurker, and this is my first post on SA - what a great crew and great advice. Thanks, again. 

For the bedding I am planning 3M 4200 (semi-permanent). Does that sound right? 

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Marelon holds up much better that the other nylon fittings you see, it will eventually get kind of crusty on the surface and the surface will flake away. The ordinary nylon ones will simply crumble in your hand. For this reason I recommend bronze above the WL (because it is impervious to UV) and Marelon below the waterline (because it is impervious to corrosion). This is opposite conventional thinking. 4200 will be fine for bedding, below the waterline I use 5200 but most would use 4200. 

But a bonded in fiberglass tube will last as long as the boat, be as strong as the boat, and never require resealing. I use G10 tube for most things, for exhaust on my boat I used exhaust tubing because is has higher temp fire retardant resin (G10 would probably work fine though). Both are pretty easy to get. If you are careful with the install, no refinishing will be required on the outside, fillet and glass on the inside. On a dirty outlet like exhaust, or a constantly dripping one like cockpit drains, you can extend the tube slightly from the transom to have it drip clear and eliminate the stains (though, that might require some external finishing to look good). 

What marina are you in?

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1 hour ago, DDW said:

But a bonded in fiberglass tube will last as long as the boat, be as strong as the boat, and never require resealing.

My first boat had the cockpit drains set up like that - solid tubes glassed under the sole and at the hull. It was a good idea - no fittings to fail and added stiffness to the boat.

Now if they had made them bigger than 3/4" ID they would have been perfect.

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1 hour ago, DDW said:

View of the ball park eh? I'm in Brickyard Cove. 

Yes, and boats that don’t ever leave the slip and may not even run, full of drunk people in orange, many nights! 

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