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Old 08-06-2013, 08:44 AM   #21
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hmm, I don't know of anyone that has posted more pictures of his boat than Mark, so I surely expect him to either link to an old post or post another pic of his super boat.

Mark -it can't be true that this is the best pic you can do....
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Old 08-06-2013, 09:25 AM   #22
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Originally Posted by Brooksie View Post
The "northsea exhaust" or a water seperator will prevent this and the former insuring that exhaust exits on the lee side.
So, your boat always leans into the wind? The lee side is higher than the windward?

Does the water discharge uphill and the gases downhill?

Will a submerged exhaust pipe offer less resistance to gas flow than one above the water?
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Old 08-06-2013, 10:33 AM   #23
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thanks for your reply mate but i was referring to an external shot of your boat showing the location of the exhaust outlet in relation to the rest of the boat
Portside, below the pilothouse, under which is the engine compartment.
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Old 08-06-2013, 03:55 PM   #24
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So, your boat always leans into the wind? The lee side is higher than the windward?

Does the water discharge uphill and the gases downhill?

Will a submerged exhaust pipe offer less resistance to gas flow than one above the water?
That's exactly the point with the North Sea type exhaust..............


I'm sure that that you are just joking, so I will follow you: yes - water will run uphill and hot exhaust gasses will naturally run downhill due to being hot

and to reply to Rick: - NO - as mentioned - hot gasses will normally exhaust downwind (depends on the force of the wind) and in a some situations the gasses will exhaust upwind or downwind (depends on the force of the wind....)
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Old 09-04-2013, 01:51 AM   #25
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Thank you very much for all the feed back.
I have moved my exhaust to the port side, exiting just above the water line, However having a hard chine hull, she tends to snap roll, this in the right combination of circumstances could flood my silencer then possible the engine.

Has anyone used a non return valve to ensure there is no flow back into the silencer.
I have seen them up to 100mm, made of steel, stainless and high pressure plastics of sorts.
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Old 09-04-2013, 03:45 AM   #26
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Definitely do something, and be sure it works. Water in an engine does not compress.
I broke the crankshaft on a small Volvo yacht (sailboat) engine. The mechanic said the engine "hydrauliced", after sailing for a long period heeled with the exhaust outlet under water, despite an exhaust trap and above water loop. Result, new engine.
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Old 09-04-2013, 05:09 AM   #27
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Frankly, with a wet exhaust, I would favour leaving it at the stern, and maybe looking to improve through the boat airflow. Our exhaust is like that, and the only time we get a bit of a smell in the boat is with a tail wind. If that happens we open the front window and get a bit of ram air through her if possible, or just close the rear door and windows, ad appreciate we are getting better speed and economy. Seldom happens tho. Not where we sail anyway. I really don't like the idea of an open wet exhaust outlet on the side where it could get submerged and water forced up it, valve or no valve...and fumes could well still come in, maybe moreso, as often the wind is on the beam. Just sayin'...
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Old 09-04-2013, 11:05 AM   #28
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Agree but not because of fumes. A single side exhaust can repeatedly roll water into your waterlift filling it and then your engine while anchored in a seaway. .
I'm a little confused as to the perceived problem. (Not the fumes...that's easily solved) If the exhaust out- let is partially in the water but the hose elbow to the water lift muffler is well above sea level, (several feet) how does the water intrude into the engine?
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Old 09-04-2013, 04:57 PM   #29
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Find out where you water line is Walt. And then see how high your turbo is above the waterline. Because that is the path it will have to take. It is likely closer than you think. I think you want a minimum of 12 inches. My boat is one of those that Cummins signed off on the installation and it is allegedly less than 12 inches although I haven't measured. It seems more than that but Timjet says his is only 9ish inches above the waterline and I think he has had damage to his turbo due to water intrusion. Just remember how low your engine is in your boat. Now if you have a "loop" or a point where your exhaust goes higher than your turbo then that helps.

It is ultimately simple physics. If the water CAN flow....it will.
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