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Moonie,

Others will probably be able to offer more technically correct advice, but I agree the exhaust doesn't look quite right. What happens if you grab the top of the pipe (near the "U") and give it a good pull to the side? What supports the last vertical run of the exhaust (from the "U" to the hull)? It appears to be clamped to something.
 

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Senior Member
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I'm wondering if the word "exhaust" is properly used... rarely see a shutoff on an engine exhaust.. I'm thinking this is a raised loop on a bilge pump discharge - but maybe not a true anti syphon loop. It appears to pass through a cockpit locker floor before going to the thruhull.
 

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Telstar 28
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I would replace those with properly installed through hulls with flanged adapters... sooner, rather than later.
 

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Sea Slacker
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1,789 Posts
I am replacing a couple of thruhulls now and will install the flange adapter (as a trial).

That said, I feel that these adapters (and flanges) are generally an unnecessary overkill.

For a test, before removing a thruhull, I pulled on the ball valve attached directly to a nonflanged thruhull (installed with the usual thru hull back nut, directly on fiberglass). I braced my feet against the bulkead and yanked the darn thing a number of times, with a force of my entire weight and then some. I haven't been to a gym in a while but I usually pull 170lbs at least (and more if I try). The point is - valve did not budge (though I bent a handle some when grabbing it carelessly :) ).

If the valve sitting on a thru-hull can withstand 170+lbs of force, I don't think it really requires additional reinforcement.

Then, as I took it apart I counted the threads that were inside the valve. This is another point usually made - thruhulls have straight thread, ball valves - pipe thread, and it is presumed that they will not mate well and for sufficient length. In this case, there were 4-5 threads inside the valve. That is virtually up to the end of valve's own threads (i.e. 2 turns more and thruhull would push against the valve's internal wall). A piece of pipe threaded tube went into the same valve exactly the same amount (5 threads) - so I am not sure whether "matching" threads would create any advantage in this either.

YMMV.
 

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Sea Slacker
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Brak

You have made some interesting points. Part of me agrees with you, the part that says that good enough is good enough. The other part-the anxious,worry-prone part, says that holes in the bottom of the boat can never be over engineered. Thanks for your thoughts!
Personally, I worry most about the hole in the bottom of my boat that:
1) is always open
2) has no devices that can be used to block water flow
3) routinely is subject to vibration, high temperature and rotational forces
4) flow of water is held back by thin rubber seal
5) difficult to access

As you may have guessed, it is the shaft seal (dripless, of the rubber ring type in my case).

As a (kind of an) engineer, I am usually of opinion that any system's strength is equal to that of it's weakest component :)
 

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Señor Member
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1,457 Posts
I am trying to figure out what the 2 fittings in the last image are for. The one with the bilge pump in between. Keel cooler?
That caught my eye as well -- particularly since the one on the left is capped off. My first thought was fresh water piping, but then remembered that this is rather deep in the bilge (duh!). The cropping is too close to see where the right one leads, or what's connected to the elbow.
 

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ASA and PSIA Instructor
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4,101 Posts
Does the exhaust exit above the waterline and is there a siphon break on the top of the riser pipe (just out of the picture?). If yes to both questions, I would not worry about the exhaust setup. If the second fitting the engine fresh water intake. Not as robust as some but I wouldn't worry about it for around town use.
 
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