A MerCruiser engine and outdrive is winterized by performing several steps, including draining the engine of cooling water and filling with antifreeze. Fogging the engine with an oily mixture, removing the battery and adding a fuel stabilizer to the gas tank are also necessary tasks.
Add fuel stabilizer to the tank and run the engine for a short time. Let the engine cool. Mix 5 gallons of gas, 2 quarts of TC-W3 two-stroke oil and 5 ounces of fuel stabilizer in a 6 gallon gas tank. Disconnect the fuel hose from the main tank at the filter and connect the remote tank's line. Run the engine for 5 minutes at 1,300 rpm. Shut down and replace the oil, filter and fuel filter.
Haul the boat or put it on a trailer so it's level. Disconnect the raw water intake hoses. Remove plugs and drain raw water. Bump the ignition without starting the engine to pump out the remaining water. On systems with air-activated water purging, use the supplied hand pump,
Replace plugs and put an earmuff motor flusher over the water pickups. Run a hose from the muffs to draw marine antifreeze from a bucket. Run the engine from the 6 gallon fuel tank until the antifreeze exits the exhaust.
Remove the battery from the boat. Do a routine maintenance inspection of the engine. Fill the fuel tank with non-ethanol fuel, or drain the tank as low as possible and add fuel stabilizer.