Drain the 2 carbs and pull the plugs and spray some fogging oil in the cylinders, then turn it over by hand a couple of revolutions Put the plugs back in. Check the lower unit for water in the grease. If it is creamy or water runs out drain and refill.
That should be all you need to do. If possible store it up right.

If you need any thing further PM sent to you.
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Those are good old motors. I have one just like it.