T&T: Onan MDJF Genset Wet Exhaust Elbow

[Bob]

I recently pulled off a badly corroded and cracked leaking wet exhaust elbow
( Part No. 155CC1059 Item No. 25, page 40 in the Onan MDJF Genset Parts
Catalog - see attached photos) and have found 40mm stainless steel
replacement parts for it... along with Stainless nipples and smaller
stainless steel piping to provide a channel for water injection into the
main exhaust pipe.  All new parts are stainless.  (see attached photos -
showing what's left of the rusted elbow compared along side the
new SS parts).  The original elbow is a one piece iron casting with a built
in water channel providing for water feed down the back of the elbow and
then directly into the main exhaust pipe at the bottom of the elbow.  I
assume that this water flowing down the backside provides some cooling of
the backside of the elbow before the water is fully injected into the
mainstream exhaust flow just below the elbow.

The Stainless Steel parts I have will assemble into a similar structure,
except the water will initially flow down a separated smaller ss pipe and
then into the main exhaust flow via a drilled and tapped hole in the ss
nipple just below where it screws into the large ss elbow.  The difference,
if any, from the original casting is that the water flowing down the
separate smaller pipe will not come into contact with the backside of the
elbow, providing no cooling of this area of the elbow, prior to being
injected directly into the main exhaust flow via nipple below... and the
point of the water injection is slightly lower (approx 20mm) than in the
original casting, which allows for attaching a stainless steel bracket to
secure the smaller ss piping to the ss elbow so none of the parts will turn
and come unscrewed due to vibration, etc..  The original brass nipple where
the water hose attaches fits the smaller piping perfectly and the inside
diameter of the brass nipple and ss pipping is about the same, whereas, in
the old cast iron elbow, the flow channel after the brass nipple seemed a
smaller diameter and seemed narrower perhaps from rusting.  The new
stainless should provide very nice water flow without any corrosion
blockage.

Onan service Manual states that purpose of wet exhaust cooling system is to
reduce temperature in Engine Room and in the exhaust gas that goes overboard.

Has anyone done anything similar to this?

Is my concern about cooling the backside of the elbow unwarranted?

Look forward to hearing any comments before I drill the final hole and
assemble and install the parts.

Thanks for any comments or ideas.

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