Exhaust Elbow - Something Clever...

[charliehows]

whoever put my boat together had some good design chops. Case in point - the exhaust elbow - which is easily 35 years old - ie same age as the engine.
Unfortunately no pic. but I'll try to use less than 1000 words. Its a 1979 yanmar 2qm20 raw water cooled engine. The exhaust manifold is standard but the exhaust elbow and lift pipe is 2" heavy steel water pipe with standard screw on bends. theres about 800mm rise after the elbow, ie above the engine and waterline, then a sharp angle down then another 400mm into the rubber exhaust. The raw water outlet goes into that 400mm section so there is no chance of any water feedback into the engine but the pipe is cooled before the rubber exhaust. Means there is no cooling on the elbow to riser top but its so heavy its never been any problem. The elbow has been off twice in 6 years, no buildup, no blockage, only a very thin layer of soot. Somehow the guys who hand built this figured a way to eliminate wear and blockage at the exhaust elbow.
Good design always makes me feel humble.

[Eclipsed]

My Atomic-4 gas engine has exactly the same set-up. It's 37 years
old and I recently replaced the manifold and exhaust elbow with the same
thing 'cause it worked for that long, it must have some merit. It was corroded but still functioning. The pipe was wrapped with heat insulation
so I replaced that also. Works just fine-temp. on outside runs about 180F.

[charliehows]

leads me to wonder if a; the manufacturer actually supplied these or specified them and b; why they subsequently changed the design to the short-lived sort of exhaust elbows most engines now seem to be fitted with.