cooling an air-cooled engine exhaust

[Ardenfour]

does anyone have any thoughts on the feasibility of introducing water cooling for the exhaust of an air cooled diesel? My existing installation consists of flexi steel pipe from the manifold, then mild steel pipe to a reliant robin silencer, then a swan neck to a skin fitting on the transom. All of this is lagged with cloth (looks like asbestos) and wound with wire to hold it in place. Then covered with tin foil. I haven't taken it apart yet, but the whole assembly is rust stained and all the lagging is disintegrating. I wondered if a jabsco type pump run off an additional pulley could somehow be used to supply raw water into the exhaust allowing me to use rubber hose for the run from engine to transom

 

[Anchorite]

I've going down this road, changing a dry exhaust (keelcooled engine) to a wet one. You need a seawater source either off a pulley or an electric pump (my choice), a water trap, a muffler and maybe a swan-neck (see Vetus catalogue), probably an anti-siphon vent (there are wet and dry types, the latter being less reliable). It's a good idea to be able to switch off the water supply just before stopping the engine (to clear the water out of the exhaust). PM if you want more!

 

[boatmike]

You either need to refurbish your existing dry exhaust or dump it completely and fit a full wet exhaust with water injected manifold exit, rubber pipe, and a waterlock. A fairly easy conversion, all parts available from ASAP supplies. Don't try to "invent" a hybrid either convert to full wet exhaust or leave it as is.

 

[ongolo]

Or as my 4 cyl Deutz is organized, run the exhaust in the oversize air duct from the engine to the outside. Where does your cooling air go out?

Regards Ongolo

 

[ShipsWoofy]

I have been involved in doing this on a couple of old Lister dumper truck engines. Presumably your engine is above the water line as it is air cooled, probably in the cockpit yes?

We fitted extra pulleys, on one of the motors we had two more pulleys fitted to drive an alternator and a water pump both items bolted to opposite bearers.

We then had a new elbow fabricated with a water inlet well downhill of the engine exhaust outlet. As the exhaust then ran down hill until it emerged at the transom we never had problems with water backing up.

It works well and is soooo much quieter.

 

[chippie]

On another forum somebody rigged up a 12V electric pump to cool their exhaust.

 

[Ardenfour]

The engine is a 9hp Ducati, mounted in the standard inboard engine position, so is probably partly below the water line. The cooling air exits via a 5" vent in the forward end of the cockpit - not an ideal location. I had thought of an electric pump but was concerned about reliability - engine's got a dynostart, which, if it packs in leaves a rubber exhaust with no cooling. My primary concern with the existing system is the hot exhaust running all the way from engine to transom. There are scorch marks on the cockpit drain pipes and several other places along the route which suggest problems in the past.