Exhaust Systems

[Vitalba]

The exhaust gases and cooling water are mixed immediately prior to the outlet of the water cooled exhaust manifold of Vitalba`s 3 cylinder Nanni.
"A". Due to physical constraints (the prop shaft) it is impossible to get the inlet of the Waterlock (Vetus LP40) much below the the exhaust manifold outlet and even so entails a sharp bend in the rubber pipe immediately after the manifold (not good as the hot gas may not be adequately cooled at that stage).
"B". The alternative and current arrangement (though not original) has the Waterlock inlet 2 or 3 inches higher than the exhaust manifold outlet but with 32 inches of rubber exhaust pipe between the two forming a `U`bend 12 inches deep. This presummably becomes the sump to take the residual water in that length of pipe when the engine is not running. From the outlet of the Waterlock to the to the top of the swan neck there is a good fall over 65 inches of pipe any residual water going into the Waterlock as normal.

Having spent a couple of days making brackets for system "A" I`m still not sure that "B" is not the better solution particularly when one takes into account a boats pitch and roll.

It may be of interest that waterlock manufacturers seem to use 10 to 20% of pipe volume as the residual water volume.

I would much appreciate the thoughts/comments of the Forum. All replies will get an A but only the top 90% A*. VITALBA

 

[Simes]

Exhaust System?

Try a different tack,

From the exhaust outlet at the engine fit a "Dry Riser" to lift the hot gases as high as possible (maybe in to an adjasent locker?) then fit the water injection point and the the flexible tube to the water trap, then out via a swan neck.

Asap can supply all of the parts, a seaflow flange to the engine then some bsp pipe work to the injection point and finally a seaflow injection elbow. All of the hardware can be of smaller bore as only gas and no water will be present untill the water injection point, then you may go back to the original diameter pipe.

Hope that this helps.

Simes

 

[Vitalba]

Simes-thanks for your reply but the the idea of a "dry riser" will not work in my case because the cooling water and exhaust gases are mixed within the water cooled exhaust manifold. It follows that any point thereafter the gas and cooling water are already mixed. The outlet of the manifold drops 45 degress for a couple of inches to the injection point thus discouraging the water from entering the engine via the exhaust valves (I hope !). VITALBA.

 

[cliffordpope]

I'd go for "B" but make a point of turning off the inlet cock and revving the engine before stopping. That would blast out any water in the intermediate section of pipe and so reduce the risk that any remaining water might gulp backwards into the engine.