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