Polaris , like Tigershark, both are discontinued brands. But right now parts are still readily available for both.
Do you have 2 different Oil and Fuel tanks. Biggest thing that goes wrong is the inline fuel/oil mixer. there are kits out there to block off the oil tank and do pre-mix in the gas tank.
Shaft bearings - Check your grease fittings on your driveshaft. If they dont look messed up/rusted out, fill them with more general/all purpose grease, or you can goto a polaris dealer and get the marine/ATV grade grease. (works the same) New grease fittings cost $3 (pack of 10, 2 of each size). first thing i did when i got my tigershark was replace all my grease fittings on the ski and trailer.
Other then that, if she starts up every time, keep fresh water flushing her and its always good to throw a new set of spark plugs in her.
Just keep in mind, Starters, Starter Benix's, go up from time to time, and carburetors usually need a good cleaning/rebuild after so many years. Rebuild kits cost around $40 (avg).
Post some pics. and welcome to the board!