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