Winterizing Mercury 4 stroke

[calveryc]

I’m about to be so busy the rest of the year that I’m going to put my boat up for the winter. It has a 90 hp Mercury four stroke so far I’ve changed the engine oil/filter, lower unit oil, topped off the gas tank with non ethanol. Is there something else I need to do? I’ve thought about putting a stabilizer in the gas tank but didn’t know if it’s necessary since it’s ethanol free.

 

[Gator]

I’ve never had a 4 stroke but definitely use StaBil in the gas tank. 1 oz per 10 gal. I would be SURE there’s no water in the motor, I’ve heard some people use antifreeze but I would check the owners manual.

 

[rusty50576]

Just let me drive it all Winter.........

 

[calveryc]

Lol well I’m hoping to get back out this winter to find some crappie but still I need to do the winter maintenance.

 

[finbully]

You can fog the cylinders. Two ways to do this:
Spray fogging oil into the intake until the engine is about to stall then shut it off and your finished.
The second way is to remove each spark plug spray a. generous shot into each hole and reinstall the plugs. Crank it very briefly but don’t start it.

Remember your battery too. Store it in an above freezing area.

 

[Fshn Cpa]

Check your owners manual. Don't know about Merc but my Evinrude has a cycle you can run and it fogs the cylinders for winter.

 

[silvertalon]

Put some stabilizer in your fuel and run the engine for 10 mins. Then trim it down and let it drain for 5 mins. All 2 and 4 stroke motors are self draining). pull the kill switch and turn the engine over for a second or two- to clear the water pump impeller. If you have a pitot hole on the leading edge of your gearcase (for speedometer), clear it out with a 9/64th drill bit as wood debris gets lodged in the hole and could trap water in the passage. Crack the lower unit drain screw and make sure there is no water in the lower unit. Milky gooey oil also indicates water intrusion (this should be done 1st before running the motor as water will have settled after the motor has been sitting for several days.). Look with a flashlight down thru the prop barrel for fishing line under the prop. Or, you can remove the prop to check. Thats all there is to winterizing a 2 or 4 stroke motor. You can still use the motor anytime but be sure to trim it down to drain and, bump it over to clear the pump- do this at the ramp when you load out. Using fuel stabilizer should be a year round practice. Especially for motors that sit around for weeks at a time. Addl; checking/changing the engine oil on a 4 stroke is paramount as water intrusion is common on 4 strokes crankcases.