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