An improved system for sealing a keel cooler to a hull of a vessel, of the type including a plurality of flow channels for exchanging heat between vessel water flowing in the channels and surrounding sea water; nozzles extending from ends of the keel cooler, for allowing the water to flow between the vessel and the keel cooler, companion fittings including at least one o-ring positioned on its inner wall, and including an opening for receiving each nozzle of the keel cooler; a bushing for allowing the o-ring of each nozzle and the o-ring of each fitting to seal against walls of each bushing; and each bushing having an eccentric circular wall, so that when the fitting openings on the hull are not the same distance apart as the nozzle openings, the bushing is rotatable to define a complete fluid seal.