Mint condition....
If its in mint condition, that may be o.k. but I'm sure, with the oil in the bilge, it is not.
Oil in the bilge could be from a leaking oil line at the rotary chamber. Standing it up to high, doesn't make sense. There could be a number of things that may have caused that oil to be there. Things that I'd be leary about too!
If you can, get a mirror and a flashlight. When you look at the ski again, use that mirror to hold down low to the bilge, aim the mirror in a way that you can shine the light onto the mirror at an angle and inspect the bottom end of the motor with a mirror.
The oil line to the port side (left) can be seen by looking down between the tuned exhaust and the engine block. It will be down toward the bottom of the block, you'll see a clear plastic line going to it. Then on the starboard side (right), look under the carbs with that mirror. You'll see the outlet line and the imprint of the round rotary valve. Check to see oil there.
Then, on the front of the engine, you have the oil line going to the oil injection pump. Make sure to put your mirror up front so that you can inspect the oil line to that pump.
If they are hiding something, they will be intimidated by your use of a mirror and may not let you take a look. If they tell you that the engine uses premix now, that's o.k., but you need to make sure that oil tank is still in place with oil in it because it needs to supply the rotary chamber with lubrication.
Last, you'll want to take a compression gage and check compression to each cylinder. You can buy this gage at any auto parts store for about $20 bucks. At any time, if they aren't willing to let you inspect this PWC, you'll need to tell them your not interested. Your compression should be upwards of 130 to 150 psi.
Your looking to invest a lot of money into something. If they will let you ride it, ride it like you've never riding one before!......then, remove the seat and inspect the engine againe. Smell inside, look it over good. Look for smoke or exhaust leaks. :cheers: