This is to give general guidelines for the winterization of inboard engines that do not have internal heat exchanger type cooling systems. Variations will become evident in different brands of engines, however the principals will be the same. Engines do not freeze. It is the water within the engine and peripheral equipment that freezes and causes damage. To preclude freeze damage you must either eliminate the water or make it so that the water will not freeze.Good steps to follow:1) Shut off the cooling water seacock if the boat is still in the water2) Open the drains on the engine block and manifold – make sure that water comes out. There is sometimes blockage at the plughole of petcock. If a water heater is involved, it too must be drained.3) When the water has drained, close the drains.
4) Remove the hose from the seacock and put it in a jug of environmentally friendly antifreeze. If easier, replace the hose with another connection to the inlet side of the sea water pump.
5) Start the engine and run it until antifreeze comes out the exhaust. Most antifreeze will bypass the engine which doesn’t matter because it has been drained. A little will go into the engine that will take care of any water that ran down from the walls inside the engine.
6) When, or if, the boat is out of the water, open the seacock to drain water from it. If the boat is to stay in the water, the seacock must be treated to prevent freezing.
Running the engine to temperature to open the thermostat and then introducing antifreeze requires that the antifreeze be at the same temperature so that the thermostat does not close when contacted by something cool.
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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