You can buy engine bright to get that old varnishy grease off. Let it sit on there an hour & rinse/spray off.
Grease in a pwc is a good thing on all metal parts, especially carbs & fuel selector. Please take it to a car wash that has a grease trap to be environmentaly conscious. Suggest you put about 5 gallons water with laundry detergent in the hull after you rinse the engine and drive around town for about 20 minutes before hitting the car wash. Pull hull rear plugs, put trailor nose up and re-rinse your hull. It will look GREAT!