As mentioned, the MD 30 engine that you have was designed and built by Volvo Penta
. The MD30 model was the lowest h.p. rating of the 30/40 family
of engines which went as high as 165 hp, so it's internal components, such as pistons, connecting rods, crankshaft, etc. were very substantial for that size engine, and will last a long time if cared for.
The exhaust elbow, #844091 is still available from VP. Early versions of this elbow were all cast iron, and subject to internal corrosion
, although they could be drilled and cleaned to maintain water
flow. Later versions had a stainless steel
liner within a cast iron outer housing and were not as subject to problems.
The exhaust tip/ reducer # 838313 is no longer available, but as its function was to merely reduce the exhaust hose size, it can be replaced by one made of stainless, fiberglass
or even cast iron pipe.