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Old 07-23-2013, 02:34 AM   #1
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Exhaust on the side

Hi all

My exhaust currently comes out under the duck board aft, the fumes tend to suck into the cabin, I am moving it to the port side about 1 m forward of the transom.

I have 2 questions?

1. should the new outlet be under, waterline center or above the water line?
2. The exhaust has a 300+ mm rise above the water line inside, will a rubber flap be enough on the side to stop swells washing up the pipe?

any and all advice would be appreciated

Thanks
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Old 07-23-2013, 03:43 AM   #2
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All the "wet" exhausts of water-cooled engines in my limited observations over the last 50 years have been above the waterline. Diesel "perfume" will vary/be present dependent on variables such as the wind direction. My boat has the exhaust above waterline on the portside, adjacent to the engine compartment, under the pilothouse. This minimizes the length of the exhaust line.





Love the sound of the water-laced exhaust of a low-RPM diesel engine.

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Old 07-23-2013, 05:32 AM   #3
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Originally Posted by markpierce View Post
All the "wet" exhausts of water-cooled engines in my limited observations over the last 50 years have been above the waterline. Diesel "perfume" will vary/be present dependent on variables such as the wind direction. My boat has the exhaust above waterline on the portside, adjacent to the engine compartment, under the pilothouse. This minimizes the length of the exhaust line.





Love the sound of the water-laced exhaust of a low-RPM diesel engine.


mate have you got any full length pics so i can see where the exhaust is in relation to the rest of the boat? ... i'll be cutting mine soon and have thought the same Q's the OP has asked

Cheers mate
Matt
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Old 07-23-2013, 09:42 AM   #4
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... i'll be cutting mine soon and have thought the same Q's the OP has asked ...
Several issues to keep in mind:

If you use a simple but cheap waterlift muffler close to the overboard you will have a cycle of dry exhaust followed by a spurt of water. The noise may be very annoying to some people.

If you run a straight dry exhaust line overboard, the noise created when the boat rolls and submerges the outlet will probably be very annoying to a lot of people.

The best and quietest systems I have seen use a muffler before the spray ring followed by a water separator. The water is discharged below the waterline and the cooled exhaust gases flow smoothly and quietly to an outlet just above the water line. The length (volume)of the system allows for a low differential pressure to develop when the outlet is submerged and greatly reduces the noise spikes. A longer run also provides more protection against waves flooding the system. Make sure the piping from the water separator is constantly down so there are no low spots to collect water.

Exhaust should be neither seen nor heard.
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Old 07-23-2013, 11:25 AM   #5
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different strokes

Rick



I love the "dry stack" exhaust system on the old boat , even if one can see it.

No its not a system to convert to in this application IMO.

Just sayin.
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Old 07-23-2013, 11:48 AM   #6
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mate have you got any full length pics so i can see where the exhaust is in relation to the rest of the boat? ... i'll be cutting mine soon and have thought the same Q's the OP has asked

Cheers mate
Matt
That's the best I've got. All that's missing in the photos are the two elbows at the top of the system.
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Old 07-23-2013, 11:52 AM   #7
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It's comforting to peek over the railing and see the water mixed with the exhaust, knowing the raw-water cooling system is working.
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Old 07-23-2013, 11:57 AM   #8
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Or you can do like Robert Beebe and have a diverter valve to the galley sink.
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Old 07-23-2013, 03:35 PM   #9
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Originally Posted by RickB View Post
Several issues to keep in mind:

If you use a simple but cheap waterlift muffler close to the overboard you will have a cycle of dry exhaust followed by a spurt of water. The noise may be very annoying to some people.

If you run a straight dry exhaust line overboard, the noise created when the boat rolls and submerges the outlet will probably be very annoying to a lot of people.

The best and quietest systems I have seen use a muffler before the spray ring followed by a water separator. The water is discharged below the waterline and the cooled exhaust gases flow smoothly and quietly to an outlet just above the water line. The length (volume)of the system allows for a low differential pressure to develop when the outlet is submerged and greatly reduces the noise spikes. A longer run also provides more protection against waves flooding the system. Make sure the piping from the water separator is constantly down so there are no low spots to collect water.

Exhaust should be neither seen nor heard.
That makes all kinds of sense for a genset, but is it practical for the main engine? Just wondering about the volume of water/exhaust gases at higher speeds.
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Old 07-23-2013, 03:51 PM   #10
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That makes all kinds of sense for a genset, but is it practical for the main engine? Just wondering about the volume of water/exhaust gases at higher speeds.
Works well on DD 2000s, 4000s and CAT 3500 series propulsion engines and a whole range of generators up to 350kW and higher. Those generators are the same size and type commonly installed as main propulsion engines on little boats.

Some higher power boats and many large yachts use a (manual or automatic) diverter valve to direct all the water and exhaust underwater at high power to keep the noise and fumes well aft of the boat. Normal slow operation is the way I described, the exhaust goes out through a muffler (optional) to a spray ring then a water separator and side or aft exhaust pipe. Some have only an aft outlet and place the spray ring near the transom.

A good marine exhaust firm can do pretty much anything you like. Most do a far better job than the production builder who builds for minimum cost and could care less about backpressure, efficiency or esthetics.
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Old 07-23-2013, 04:08 PM   #11
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Works well on DD 2000s, 4000s and CAT 3500 series propulsion engines and a whole range of generators up to 350kW and higher. Those generators are the same size and type commonly installed as main propulsion engines on little boats.

Some higher power boats and many large yachts use a (manual or automatic) diverter valve to direct all the water and exhaust underwater at high power to keep the noise and fumes well aft of the boat. Normal slow operation is the way I described, the exhaust goes out through a muffler (optional) to a spray ring then a water separator and side or aft exhaust pipe. Some have only an aft outlet and place the spray ring near the transom.

A good marine exhaust firm can do pretty much anything you like. Most do a far better job than the production builder who builds for minimum cost and could care less about backpressure, efficiency or esthetics.
Interesting - thanks RickB. Always fascinating to hear about technically "pure" solutions.
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Old 07-24-2013, 08:39 AM   #12
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All the Eagles thru hull are above the water line except for the raw water in take for the e.gines. The exhaust is also above the water line. The Eagle was dry exhaust but was hot and noisey. Converted to wet which cooled and quieted the exhaust. Had a modified water muffler the gravity drain made an install at a local muffler shop. Any way thru hulls and exhaust above the water line.

As for side exhaust when the wind is blowing right you will still get fomes. The cheapest and easest is change the course. I been burning the newer ultra sulfur diesel mainly for thr diesel boilet which burns very clean. I can stand in front of the boiler exhaust, and NO sutt.
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Old 07-24-2013, 09:29 AM   #13
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I also get exhaust fumes, being raw water cooled and therefore running a low engine temperature, the engine is probably not burning as cleanly as some.
Surprisingly it is worst is when I am heading directly into the wind.

The best solution I have found so far is opening the forward facing cabin windows and hatches to get maximum air flow out the cockpit door. This minimises any backdraft which sucks the diesel fumes into the cockpit.
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Old 07-25-2013, 05:15 AM   #14
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As for side exhaust when the wind is blowing right you will still get fomes. The cheapest and easest is change the course.
Or have a North Sea type exhaust - which exits on both sides of the hull - so the fumes will most likely exit on the down wind side.
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Old 07-25-2013, 05:46 AM   #15
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I guess that would work if your boat always leans into the wind.
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Old 07-25-2013, 05:48 AM   #16
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I think that the water from the exhaust will always exit on the leaning side - and I think the the exhaust fumes generally will exit on the downwind side - I haven't used the system so I am guessing.
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Old 07-25-2013, 11:47 AM   #17
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Or have a North Sea type exhaust - which exits on both sides of the hull - so the fumes will most likely exit on the down wind side.
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. The "northsea exhaust" or a water seperator will prevent this and the former insuring that exhaust exits on the lee side.
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Old 08-06-2013, 08:10 AM   #18
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That's the best I've got. All that's missing in the photos are the two elbows at the top of the system.
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
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Old 08-06-2013, 08:15 AM   #19
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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. The "northsea exhaust" or a water seperator will prevent this and the former insuring that exhaust exits on the lee side.
Agree, but this problem can be eliminated by installing a waffer type valve - basically its a simple valve that can be closed with a lever when leaving the boat.
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Old 08-06-2013, 08:30 AM   #20
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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
Basically, the further away from windows, door openings or hatches the better - obviously, the further aft is usually better.

But - if you install the dual exhaust North Sea type then it doesn't really matter since the exhaust fumes will (most likely - disclaimer) exit on the downwind side.
But - if - on a downwind leg, then it might even be better to have a forward exhaust, since the gasses MIGHT blow ahead of the boat.....
Just saying that there is no perfect system...
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