Winterizing Mercury 150 Fourstroke

Got some friends in the DFW area that are looking at purchasing a pontoon with a 2021 150 fourstroke merc on it.

They were asking me how to winterize the engine and it occurred to me in all my years of owning a bass boat I never winterized the engine (we fished a lot in the winter and when there was a freeze warning we put an electric blanket on the engine).

I watched a few vids on youtube but most appear to be from up north. I assume just a full fluid change, trim it down and get the water out of it then maybe pull the plugs and spray inside them?

Boat will be stored on a trailer and outside during the winter.

Any input on this is appreciated.

Sounds good for me. I’m like you, my boats used every week year round.

I always change the lower unit fluid before it freezes. This just reduces the chance of freeze damage. Having the motor stored vertically where it will self drain will take care of the rest. If I was putting it up for long term storage then fogging the cylinders would make sense.

I usually do my 100 hour service in the fall at the end of the “season”. I still fish in the winter some but usually hunt from October until January and the boat sits. Doing the service in the fall just makes sense to me.