Winterizing Your Fresh (internal) Water Cooled Inboard Engine
by Gordon Torresen

This is to give general guidelines for the winterization of
inboard engines that have internal, heat exchanger type
cooling systems. Variations will become evident for
different brands of engines, the principals will be the
same. Engines do not freeze. It is the water within the
engine and peripherals that freezes and causes damage. To
preclude freeze damage you must either eliminate the water
or make it so that it will not freeze.

Good steps to follow:

1) Check the specific gravity of the internal coolant.
Antifreeze checkers are widely available, and very cheap.
Depending upon your location, be assured that the freeze
protection is adequate. If protection is marginal, either
drain some off and add 100% new or change the whole lot.
Antifreeze should be changed every three to five years,
according to Yanmar and the AF makers.

2) Shut off the sea water intake sea cock, if the boat is in
the water.

3) Take the hose off the seacock and put it into a jug of
environmentally friendly antifreeze. It is sometimes easier
to remove the hose at the pump and use a different hose into
the jug.

4) Start the engine and run it until the antifreeze comes
out the exhaust.

5) Reinstall the hose to the seacock.

6) Reopen the seacock after the boat is hauled. If the boat
is to be left in the water, the seacock may require
winterizing, again depending on the severity of your winter.

If you are not located where winterizing is required, read
this through and purr.

It is highly recommended that if the lube oil needs to be
changed that it be done prior to lay-up so that fresh oil is
coating the innards of the engine. If fuel filters are in
the plan do them first. Then start the engine to check the
fuel filters and warm the engine to facilitate the oil
change.

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