Abstract: An apparatus for flushing the cooling system of a marine motor is disclosed. The apparatus includes a catch basin having an immersion pump located therein. A pair of suction cup sealing members, joined together by a U-shaped spring, are placed over the coolant intakes of the motor. One of the suction cups communicates via a hose with the immersion pump. The immersion pump is supplied with electrical energy either from the water craft's on-board battery or from an auxiliary battery. The catch basin is filled with a quantity of anti-freeze solution and the immersion pump and the motor are turned on in that order. The anti-freeze solution is then repeatedly circulated through the engine cooling system and is discharged through the engine cooling system outlet back into the catch basin.