Air cooled engine with wet exhaust? - SailNet Community
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post #1 of 41 Old 01-16-2012 Thread Starter
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Air cooled engine with wet exhaust?

Hi there,

My girlfriend and I recently invested our lives and money into a sailboat. Our goal of cruising towards Cuba has unfortunately come to a bit of a standstill as some of the current realities with our boat have made themselves seen.

We are now in Beaufort, SC - and time has come to make some tough decisions. I would hate to say stuck, as it is a wonderful town!

The boat is a beautifully crafted George Buehler steel cutter. Not just a home build either - done by professionals at a boat yard. We are still very happy with the purchase. Incredibly solid - built to face almost anything. BUT, there are some quirks that need to be worked out before we can move forward.

The main one being our exhaust system. We have a Deutz 303-1 air cooled engine. Everything I have read and researched about Deutz engines has been positive. It is a little bit underpowered for our boat weight - but nothing that cant be managed. All in all - the engine is in great condition, runs really well, and I'm happy with it.

Unfortunately, the show stopper at the moment is the exhaust system that was coupled with the engine. A dry exhaust runs to the stern of the boat. Whoever installed the dry exhaust seemed to have known what they were doing - but it seems to be a poor match with this engine. It is a rather long (too long) system of flex pipes, metal tubing and muffler. We are not happy with it at all. The engine is a bit of a beast, and as a result, the exhaust system rattles and shakes. Rattles and shakes to the point that leaks have developed. We dont think this a problem that can simply be addressed by getting new parts. I'm convinced that the fate of the new parts will be the same in the long run. My opinion is that we will need to switch to a wet exhaust.

I'm wondering if any of you have experience with, or thoughts on matching an air cooled engine with a wet exhaust. The main concern I have is with the length of the exhaust system. In all, it is just under five feet in length, and from what I understand of wet exhausts - the shorter the better. We have no above the waterline seacocks on the port and starboard side of the boat, so the exhaust pretty much has to go out the stern.

We would love to keep the momentum of our trip going.... but things need to be dealt with.

ANY help would be much appreciated.

Cheers
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post #2 of 41 Old 01-16-2012
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Deutz engines run as long as you feed the diesel. They are very reliable but they make a lot of noise. A wet exhaust might decrease the noise but, the engine noise will always be there. Air cooled engines and specially Deutz is always more noisier than a water cooled engine. Try to replace your engine with a water cooled one, otherwise you will not benefit too much from an exhust with water.
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post #3 of 41 Old 01-16-2012
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Its a completely air cooled engine ?

Its got to get awful hot in there

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post #4 of 41 Old 01-16-2012 Thread Starter
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Right now, my concern isn't with engine noise. Both of us can manage to live with that. We plan on sailing our boat more than motoring for the most part (unfortunately, January North Atlantic weather dictates otherwise at the moment). Our concern is with the exhaust. Said exhaust leaking into the cabin is not something we can live with (pun intended...).
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post #5 of 41 Old 01-16-2012 Thread Starter
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The engine is fully air cooled. The duetz is designed that way, and seems to do a good job at it. I have no concern with it overheating. We also have a blower that runs more air to the engine - but this isnt necessary at the moment, as the cool Jaunary air does a good job at that. All we have to do is open a hatch.
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post #6 of 41 Old 01-16-2012
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On the dry section of my exhaust we just wrap the heck out of it to try and keep it at a civil temperature to try and not start a fuel fire should there be a leak

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post #7 of 41 Old 01-16-2012
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I would think the length of a wet exhaust would be the same as the current dry one. If so, the only way to reduce the pressure loss would be to either straighten it out to reduce bends or increase the diameter. If you went with a new wet system, you would need a small water pump (electric would be the easiest) and a water lift muffler. After the water injection point, you could then use exhaust hose. Seems doable, but you have to consider that the water injection system is going to add some complications and maintenance issues.
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post #8 of 41 Old 01-16-2012
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Brent Swain has popped up on a thread about Ganley boats in the Review & Purchase forum. If anyone knows how to do this cheap and well, it would Brent.

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post #9 of 41 Old 01-17-2012
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Wet exhaust should work fine

You must take the same considerations as on a water cooled engine to prevent water flooding the engine.

I did a similar ting once - this boat originally had dry exhaust going over the wheelhouse roof.

We made a dry muffler that also worked as a water lock (preventing water entering the engine through the exhaust). We welded an water injection bend and attached the flexible rubber exhaust pipe to it. The purpose of this was to
a) be able to use a flexible rubber exhaust hose
b) cool the exhaust before going through the hull (wooden boat)

You must look for an arrangement where you can inject water into the system at point w/o risk of back flooding the engine. from that point you can use rubber exhaust hose.

There are flexible tubes around that can be used for dry exhaust - do you have this in your existing system?

Any pictures / drawings showing existing arrangement?

Last edited by knuterikt; 01-17-2012 at 02:05 AM.
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post #10 of 41 Old 01-17-2012
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I must be missing something here. How does an air-cooled engine get a wet exhaust? Are you talking about pumping raw water from overside into some sort of injection elbow just to cool the exhaust gases?

If that's the case, why bother? I've seen plenty of dry stack exhausts on V8 engine fishboats. Double tubing them and lots of lagging where there might be any contact with anything works just fine - why bother with pumps, through hulls etc?

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
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