Abstract: An agitator includes a drive motor having a shaft projecting through an axial end of a housing and having connected thereto a propeller boss. The propeller boss and housing define a circumferential gap spanned by a circumferentially extending radially outermost gap covering and sealing portion of a deflector ring. The deflector ring includes a radially innermost ring mounting portion located in the circumferential gap. The deflector ring is preferably made of elastomeric material and an outermost circumferential surface of the deflector ring is exteriorly convexly curved in the form of an aerofoil converging axially toward ends of sealing lips of the deflector ring gap covering and sealing portion.