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Top Winterizing Tips
“Fogging” means applying lubricating oil to cylinders and pistons while the engine is running. This can be sprayed in via carburetors or air intakes, or a special mixture can be supplied to the engine via a portable tank connected to the fuel line.
Flush and Drain
Flushing the engine’s cooling system with fresh, clean water is usually done at the same time as running the engine to distribute the fuel conditioner and fog the engine. Again, the savvy winterizer thinks ahead: The engine needs to be hot for the oil change, so that is done first, before flushing and finally fogging and filling with antifreeze.
When flushing, adhere to the manufacturer’s instructions. Flushing the engine, especially before a long layup, is crucial to its long-term survival — notably if you run it in salty, brackish, silty or otherwise dirty water.
When done, all water should be drained from the engine and drive to reduce the chance of freeze damage. Outboards can be drained simply by trimming them to the full-down, running position. Allow all the water to drain from the power head through the propeller and/or exhaust outlets. Sterndrives should also be stored trimmed down, though it’s prudent to remove the drive to check the bellows, gaskets and other gear, in which case it’s best to store the drive inside.
Newer sterndrives and inboards have three or four block drain plugs; here is where a service manual is almost a must. Your engine may have block drains, exhaust manifold drains, power steering cooler drains, oil cooler drains and/or fuel canister drains. Be sure to remove them all or freeze damage could occur.
Older sterndrives and inboards typically have brass drains in the lower crankcase and also in the bottoms of the exhaust manifolds. Often, these can get clogged with rust flakes and debris from the cooling passages. A small wire or a pipe cleaner must be run up inside these drains to loosen any debris to allow water to drain. Don’t stop probing them until you are sure all the water has drained.
Regarding inboards and sterndrives with closed-loop freshwater cooling systems: Drain and change the coolant because, over time, coolant will lose its anti-corrosion properties.
For the raw-water cooling circuit, if yours has a freshwater flush connector, use it. If not, close the intake seacock and disconnect the hose on the outlet side of the raw-water pump. Disconnect the cooling-water discharge hose from the exhaust manifold or riser. Next, run fresh water into the discharge hose to back-flush raw-water passages and rinse out salt deposits. Make sure all the water drains out.
To prevent corrosion and freezing from exposed metal or any residual water in the engine block of a raw-water-cooled engine or the heat exchanger of a fresh-water-cooled engine, take the following general steps, using your service manual as the final guide. Reconnect the water-pump outlet hose. Pour a 50/50 mix of propylene glycol antifreeze into the disconnected discharge hose until the hose is full. Allow the mixture to remain inside the block for several minutes. Open all raw-water drain plugs and drain the engine. This treatment leaves behind a layer of corrosion protection on the internal surfaces and keeps water that might be left inside the engine from freezing.
Remove the raw-water pump’s impeller. Antifreeze swells some rubbers, so rinse the extracted impeller as a precaution. Some boaters grease the impeller and reinstall it. This is fine, but I like to leave it out until spring so the vanes don’t take a set.