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    Please remember that these pictures are basic - each manufacturer has their own system, but with these pictures you should be able to understand how each system works.

    There are three basic systems used. The full loop system, the half loop system and the raw water system.(they may be known by other names e.g. seawater system or closed looped) Each system is used for a specific purpose but it all boils down to money. The more money the better the system.

    The full loop system is the cream of the crop (most expensive) - and will have very little sea water damage over the years of use. This system allows the engine to operate at higher and more efficient temperature.

    The half loop system is the second best but exhaust manifolds and risers are subject to sea water damage. This system lets the engine operate at a higher more efficient temperature as well.

    The raw water system is the cheapest and most common system used and subjects the engine and manifolds to sea water damage. Designed for fresh water use. This system operates at a lower operating temperature to reduce calcium and scale build up inside the engine from the minerals in the water.

    In reference to the pictures:

    1 - Raw water strainer - To keep debris out of the cooling system. Some strainers have drains some donít. Some strainers are built into the out drive. Some are just a grill mounted in the hull, and some strainers are a complete unit that is mounted in the engine room.

    2 - Raw water pump - supplies cool water to the engine and can be part of the outdrive or a separate unit mounted and driven by the engine. Some raw water pumps have drains but most engine mounted pumps donít. Those that donít have drains are to be taken apart and inspected when winterizing. Most outdrives will drain themselves but there are some that have to be inspected to winterize.

    3 - Cooler - to cool oil - can be a transmission oil cooler - an engine oil cooler - a power steering oil cooler - a fuel system cooler or a combination of any or all. Some have drains, some donít. Those coolers that donít have a drain will need one of the hoses removed to drain the water out.

    4 - Heat exchanger - Takes the engine heat and transfers it to the raw water system.
    Most will have a drain, some will have a drain for the raw water and a drain for the engine coolant.

    5 - Engine - The engine coolant is used to remove the heat produced by the engine. The engine has its own circulation pump to keep the coolant moving through the heads, intake manifold and the block of the engine. On the raw water systems, the engine block has to be drained to winterize.

    6 - Exhaust Manifold - These are water cooled to keep the heat down in the engine room. Raw water and half loop systems must be drained to winterize. The riser should drain with the manifold. On full loop system the riser will usually self drain but not always.
    Attached Files

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