It's a good idea to change oil before storing a watercraft over winter. Combustion contaminants in the oil can attack the metal. It's best to have fresh oil when sitting for a long period. Also the interval per your manual is 100 hours or 1 year.
True, but that's where today's synthetics EXCEL, not absorbing moisture and remaining consistent for L O N G periods. Doubtful our machines get many "short trips" and most - if any combustion byproduct is burned off, especially at the RPM's these run. If anything, change "fluids" on a "vehicle" at shorter intervals when newer as metal "finds it's finish" over the miles/hours. I think stored in a warm garage, a synthetic can easily maintain it's proportions for two years about 75~ hours, but, I like to change earlier on the first change, whether a motor or boat vehicle to get initial wear in out of the lubrication. Now, I'll probably go two years before changing again, then at year three, take the cover off and go through it all, with plugs, et all at that time...coolant at year 5..
I noted my machine "used" about 1/2 pint of coolant, though I believe most of it spalshed out the overflow tube on the waves/rockng etc., over the summer. Still, I topped off to the full/cold line with XPS coolant (not knowing what formulation this coolant actually is- and there are so many used today) costing $13 qt! Lots of XPS spray on all the petal and pivots. nice detailing and a wax too. Leaving the access doors off and battery tender connected, I'll test batt voltage monthly and recharge as needed, can't wait till April!