Diesel wet exhaust without a muffler

I am 12 months into a refurbish project for a 1972 Bristol 34 sailboat. I don't motor much (20 hours in 1 year), so the engine hasn't been high priority until now. In reviewing the wet exhaust design for the Westerbeke W27 diesel, I see that it does not include a silencer or muffler. It appears that the 12 foot long (approx) upward slope exhaust hose acts as the water baffle. I have never seen this before, and can't find any reference to this type of design. Does anyone know the trick here? Is there a right way and wrong way to not use a muffler?

 

I recently returned from a 2 year trip south on the bristol 34 and prior to departure installed a westerbeke diesel. I now have around 600 hours on the engine and have had some problems. The cooling for the transmission will chafe from the vibration of the engione and according to testing doesn't need to be there at all. I spent a long time and lots of money to have it installed only to remove it 200 hours ago with no change. I was able to get the water lift muffler from westerebeke to fit in the bilge. however when attached to the engine and run out the transom the exhaust water will back flow through the engine causing severe problems. I had to exhaust over the side of the boat necassatiating the use of a 2.5 inch ball valve on the exhaust when the engine is not running. Please let me know if you find an alternitive and what you do/did about the trany.
Jud Cleveland
Portland Maine
coastaldesigngroup@earthlink.net
or judandpay@hotmail.com

 

Bristol 34 wet exhaust

I am uncertain if you have the same Westerbeke W27 4 cyl engine as my boat, but I'll assume it's not a W27.

My engine sits very high in the compartment, with the head about 6 inches below the cockpit sole. The exhaust system has no separate muffler chamber, but instead relies on only the large (3 inch?) exhaust hose to do the equivalent job. The hot water hose exits the heat exchanger and loops up as high as possible before entering a larger pipe T where the water and gas are mixed. This T is about 8 inches below the cockpit sole. From there the large exhaust hose (now carrying the water-gas mix) drops aft toward the hull (port side, beside the fuel tank) and then follows the hull shape up towards the transom. The hose enters the lazarette on the lower port side,then rises as it crosses the boat to stbd such that the hose peaks just below the aft deck. The hose then drops down to the exit point at the lower tansom on std side. This system works well for me and I have not had any backflow problems. Perhaps you need the 2 high points as is generally recommended for wet exhaust installations.

My small Hurth transmission does not have a separate cooling system. I have run it no longer than 2 hours at heavy load, but I noted no problems other than a hot engine compartment. My transmission doesn't always quickly go into gear, so I always shift between fwd and reverse while maneuvering (avoiding neutral). It always goes directly from one gear to another, but either gear from neutral sometimes takes 4-8 very long seconds.

I also have a very slow coolant leak (a few onces per hour) that I have as yet not located. I just add coolant every few weeks during the season.

BTW, you can visist www.artzat.com/gusto to see some before-after images of my boat.

Good luck.

Arthur Zatarain
arthur@artzat.com
www.artzat.com