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Winterizing a 4 stroke outboard


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Yep not much to it, I had a 25 Yamaha on my old pontoon, I would fog it it in the water then pull the boat and tilt it up and down a couple times, leaving it in the full down position for storage, I kept the battery on a trickle and turned the motor over every 5-6 weeks but didn't try to start it. (This is something recommended on line by a lot of outboard owners not sure it's necessary).
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I'm not real familiar with the procedures for a 4-stroke but I've been winterizing 2-stroke outboards for over 40 years. I'm assuming here the engine is carburetted. The first thing I'd do is run the engine out of gas while squirting some fogging oil into the carb. That will make sure you don't have gas sitting in and varnishing up the float bowl and jets and you will get a bit of fogging oil coating inside the carb and intake side of the engine. Do this while the boat is in the water or out of the water with a set of ear muffs supplying water to the intakes.


Once the motor is out of the water, tilt it up and down to make sure the water is drained out of the engine jacket and water pump. You don't want any water freezing in there.


Unless you're using a special gearcase oil that's rated for multiple years use (like the expensive stuff Bombardier makes for Evinrude E-Tecs which you can leave in for 3 years) I would drain the gear oil and replace it with a fresh batch and replace the seals on the top and bottom gearcase screws. It may not be totally necessary to do this every year but the oil is cheap compared to the cost of the motor and a gearcase overhaul so why take the risk that some water got in there over the summer?


I would also take all the spark plugs out and spray a bit of fogging oil into each cylinder while rotating the flywheel. That will coat the top end of the combustion chambers with oil and prevent them from becoming corroded.


Clean the plugs, check the gaps and put them back in to the correct torque (or put new ones in if the old ones are worn) so the motor is ready to go for next year. That should pretty much be it except also filling up the portable fuel tank full to eliminate headspace in the tank and adding the correct amount of fuel stabilizer for the amount of fuel in the tank. I also always take a little bit of grease and lightly grease all of the hinge points on the throttle and gear shift linkages using my finger tip. If you've got any grease nipples on the motor, give 'em a little shot of grease with a grease gun too.


This is the process I've followed for over 40 years with my outboards and since I've had two that have lasted me 40+ years without any sort of storage, linkage or gearcase related problems, I'd say these procedures have worked really well. I know 4-strokes are fair bit different at the top end but I think all or most of these procedures should work just as well for them as they do for a 2-stroke.


Just as an added note, I now run an Evinrude E-Tec on my runabout/ski boat and it fogs itself. All I have to do is change the gear oil and screw seals once every three years. It's awesome. ;)

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