On an outboard, really not much to do
http://www.bassboatcentral.com/winterizing.htm
Don't know what part of the country you're in, but I don't remove my batteries - I leave them on the charger (newer Noco) which keeps batteries in float mode if it doesn't need a charge. On my boat, when I installed a water pressure gauge, I added a T valve so I can drain the water prior to winter season. One thing they didn't say - LEAVE THE MOTOR DOWN - do NOT tilt it back up. This lets water/snow drain and doesn't allow it to collect and freeze.
Now prior to using it for spring, there's a LOT to do for prepping for a season hassle free startup. Water pump impeller change, lower unit check to verify everything is good there. Fire it up on muffs and let it warm up at idle. Check EVERYTHING, besides the engine, there's a lot to check on the boat. Check all gauges for function, all fuses are good, batteries are good and connections corrosion free including your switches, connections in/around the console, all lights function, horn work etc etc etc.
Since you recently got this motor, and it sat for so long - did you replace ALL fuel lines, filters from INSIDE the tank to everything on the motor. Has the carburetors been cleaned and a sync & link procedure done? Fuel lines deteriorate quickly from ethanol use if you do not get the proper marine fuel lines.
I like Sta-Bil Storage for winter use
I also follow this recommendation
Fuel Additive Recommendations:-Stabilize fuel ANYTIME fuel will not be consumed and replaced within 15 days!!!
-Optis (ALL, including XS & ProXS): Quickleen in EVERY TANK OF FUEL. You CAN combine Mercury QuickCare or QuickStor Fuel System Treatment & Stabilizer (or Sea-Foam if you prefer it) with Quickleen. Use the recommended "dose" of each product per the bottle instructions. For anyone questioning Quickleen recommendation- see Service Bulletin 2001-12 (yes, it's been recommended since 2001!!!).
-Quickleen may be used in ANY Mercury engine- it helps to prevent/remove carbon buildup (primary purpose).
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"Mercury Component Cocktail" (Chemically, this works much the same as the previously recommended (and now to avoid alcohol content) cocktail, and requires less components.) This is Don's Preferred "Cocktail":
-1oz Mercury QuickCare per 5 gallons fuel
-1oz Mercury QuickLeen per 5 gallons fuel
(If leaving fuel in boat for more than 30 days, be sure to also add Mercury QuickStor).