Cooling system: New engines have closed freshwater cooling systems. These in turn are cooled by raw water and may require a greater volume than did your old engine. An inadequate supply of raw water can lead to overheating, so to be on the safe side, if you find you need a bigger inside diameter on the cooling hose for the raw-water pump, you should upsize all components in the system. For example, some ball valves at through-hulls have a smaller inside diameter than adjacent piping and can cut flow by as much as two-thirds. Between the seacock and water pump, use reinforced marine-grade hose that wont collapse. Protect the hose against chafe, and double up stainless-steel hose clamps. Get rid of fine screens outside the hull that can clog (a bronze grate is fine); its sufficient to install a good seawater strainer (if its bronze and stainless steel, protect it against galvanic corrosion). Youll likely need an anti-siphon valve before cooling water enters the exhaust mixing elbow (see "Help Your Engine Keep Its Cool," February 2002, for more cooling-system details).