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  #1   IP: 75.142.49.80
Old 03-11-2013, 03:37 AM
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General question about exhaust system

i occurred to me today that don't know why it is conventional to mix cooling water with exhaust gas. It seems like it causes problems. Why not just have a conventional muffler, and run the water straight out?
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Old 03-11-2013, 07:39 AM
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Marian Claire Marian Claire is offline
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I think the short answer is heat. How do you have a water tight exit port for a pipe that is several hundred degrees without damaging the fiberglass or wood hull/deck? Dan S/V Marian Claire
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Old 03-11-2013, 08:28 AM
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Talking

If you can fit a pipe straight up amidships with a shroud, you can do it like a commercial fishing vessel.
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Old 03-11-2013, 09:48 AM
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Plenty of boats do use dry exhaust. They tend to be commercial boats that don't mind the heat and noise. Pretty much the entire crab boat fleet is that way and those things will wake up an entire anchorage at 0500. Of course they'll do a few close passes to make SURE you don't sleep in
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Old 03-11-2013, 07:47 PM
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Curious about Halcyon - glass over mahogany as original or was that a refit?
How about the house? How about a photo (or 2 or 6)?
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Old 03-12-2013, 02:04 PM
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Quote:
Originally Posted by Al Schober View Post
Curious about Halcyon - glass over mahogany as original or was that a refit?
How about the house? How about a photo (or 2 or 6)?
Original. Nicely done too. Quite an unusual boat. I rescued her from where she'd been lying at Dana pt after the owner builder died 12 years earlier. Beautifully built solo by a German emigre engineer who worked for NASA on the Apollo program. Custom stainless work done in the NASA shop, bits of apollo on her. He had the hull designed by naval architect Brendlmeyer who was in Vancouver I believe - now deceased. I tried to contact his heirs but didn't get much of a response. I believe my hull design was scaled down and became a small class (of 28footers) around Vancouver. If anyone knows anything about this I'd be pleased to know. When I bought the boat from his widow, she said they'd recently dumped two garages full of boat junk, including 1:1 drawings. I wept!
Re pics, Its a work in progress, things like job and family have gotten in the way of bringing her back, I aim to haul the mast soon - all the varnish was blown off years ago. An aging A4 is just one of my ongoing projects I'll see if I can post some pics soon.
Simon
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Old 03-12-2013, 02:09 PM
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Quote:
Originally Posted by Marian Claire View Post
I think the short answer is heat. How do you have a water tight exit port for a pipe that is several hundred degrees without damaging the fiberglass or wood hull/deck? Dan S/V Marian Claire
Thanks all for reports on exhaust. Heat, noise, all makes sense. But the down side is all this trouble with exhaust systems, rust, water backing up, etc. Has anyone tried hooking up a normal (ss) automotive muffler? If one could solve the hot pipe issue, which I'm sure is solvable more elegantly than crab boat style, it might be a great simplification (?)
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Old 03-12-2013, 03:14 PM
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I saw a boat for sale with dry exhaust out the stern. They fabricated an outer and inner pipe and had an industrial blower running air in the space to keep it cool. What you are neglecting is 99.99% of dry exhaust boats use a vertical exhaust. Ever see a cargo ship with exhaust run out of the stern........didn't think so. You STILL have to make a water trap of some kind if running a horizontal exhaust.

Quote:
Originally Posted by HalcyonS View Post
Thanks all for reports on exhaust. Heat, noise, all makes sense. But the down side is all this trouble with exhaust systems, rust, water backing up, etc. Has anyone tried hooking up a normal (ss) automotive muffler? If one could solve the hot pipe issue, which I'm sure is solvable more elegantly than crab boat style, it might be a great simplification (?)
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Old 03-12-2013, 03:42 PM
JOHN COOKSON JOHN COOKSON is offline
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Durn Right

Quote:
Originally Posted by joe_db View Post
Ever see a cargo ship with exhaust run out of the stern........didn't think so. You STILL have to make a water trap of some kind if running a horizontal exhaust.
Running the exhaust straight from the engine to the back of the boat won't work. Any following seas will end up in the exhaust system and the engine. There has to be a vertical rise somewhere. A one way flapper valve might work but I wouldn't trust it.

TRUE GRIT
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Old 03-14-2013, 03:38 AM
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" Any following seas will end up in the exhaust system and the engine."

no doubt! A vertical riser is needed. but water mixing isn't. I now understand why the water lift muffler, even though I still think there might be an alternative. In any case, thankyou all for contributing to this thread. No need to continue it
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