Winterization of Mercruiser Inboard & Sterndrive Engines
With winter coming, winterization of your MerCruiser® inboard boat engine is extremely important. But, before you get started, we really can’t understate the importance of knowing more about it, especially if you are a die-hard do-it-yourselfer.
Winterization of MerCruiser® Inboard Engines
Service Manual – It’s highly recommended that you have a factory service manual handy to locate all the drain ports and cooling units on your motor. The MerCruiser® manual has a very detailed section on winterization procedures. If you don’t have the original manual, you can order Mercury® literature online or you can get a copy through any authorized dealer.
Tools – You’ll need screwdrivers, sockets and wrenches to do your winterization quickly and efficiently. It’s a wise idea to read through your service manual before you get started for more details. The manual will point out any special tools that’ll be necessary to complete the job without interruption.
Supplies – You’ll need to have drain plug gaskets, an oil suction pump, an oil filter and enough motor oil to completely change the oil in your motor. You’ll also need a can of fogging oil and several gallons of propylene glycol based RV antifreeze that also contains a rust inhibitor and a good quality fuel stabilizer. Additionally, you’ll need lower-unit lube and a lube injection pump.
The Procedure –
- Start by pumping the oil from the engine. Once it’s completely drained, change the oil filter and refill the engine with the recommended oil viscosity.
- Add fuel stabilizer and run the motor either in the water or by using your garden hose and a bucket or tub with a 50/50 solution of antifreeze and water. Check your service manual to see what the manufacturer recommends for you particular motor.
- Remove the spark arrester from the carburetor and fog the motor by following the directions on the can.
- Drain the hull. Instead of opening the petcocks, remove the hull plugs. This will allow the hull to drain completely and eliminate the possibility of twisting off the petcock wings.
- Starting at the top of your motor, remove the drain plugs and hoses for the exhaust manifolds, power steering and oil cooler, as well as the block drain plugs.
- Leave the block drain plugs out and set them aside for safe keeping. Re-install all the other drain plugs with new gaskets and re-install the hoses. Give everything a once-over and replace worn-out or parts that are of questionable quality.
- Next, remove the thermostat and housing and add antifreeze until it drains through the entire block. When the antifreeze has drained completely, re-install the block drain plugs.
- Some marine engine manufactures recommend leaving the engine block empty for the winter. However, other makers recommend filling the engine with antifreeze. It’s always a wise idea to follow your engine manufacturers specifications.
- Next, it’s time to lube the lower unit. You’ll want to do this to make sure there is no water in the lower unit that will freeze and cause any damage. Simply remove the upper and the lower drain plugs. Wait for the oil to completely drain out. With the upper plug out, use the lube injection pump to refill the lower unit until oil starts coming out the top vent. Replace the gaskets and re-install the upper plug first and then the lower plug.
- Finally, check over all the wiring to be sure it is in good order with no wear spots or loose connections. Some boat owners also choose to spray the wiring and electrical system with a silicone protectant and remove the battery for storage inside. Be aware that batteries can create a fire hazard from being charged in a confined area.
Although this is not an all-inclusive checklist for winterizing your inboard motor. When in doubt, the original service manual should always be followed. This list is also what you would expect from a reputable authorized service dealer in the event you choose to have the work done by a professional.
Disclaimer – We all enjoy doing some of the work ourselves, however we highly recommend that all precautions are taken. Any damage caused by improper winterization and freezing will not be covered by your warranty.
To talk more about winterization techniques, MerCruiser® motors or other boat motors for that matter, please contact us. Our staff will be more than happy to assist you any way we can.
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