said concavity at said trailing end of said concavity having a depth sufficient to accommodate said impeller such that {HEAD ~ a central hub} of said impeller is positioned at {TAIL ~ an elevation} substantially equal to an elevation of said output shaft of said engine 
is positioned at
said concavity at said trailing end of said concavity having a depth sufficient to accommodate said impeller such that { HEAD ~ a central hub } of said impeller is positioned at { TAIL ~ an elevation } substantially equal to an elevation of said output shaft of said engine
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH