Heavy duty construction for both commercial and pleasure boat use. Exclusive permanently lubricated "ball-bearing" motor results in longer motor and seal life, lower amp draw, lee motor drag, lower motor temperature. Ignition protected. Double insulation reduces possibility of shaft electrolysis. Water cooled motor for longer life. Heat resistant Acetat resin housing provides strength and impact resistant. Moisture tight seals. No burn-out when run dry. 5/16 stainless steel shaft. Easy "snap-on-snap-off"