I bought a Seadoo RX once from a local dealer,it had low compression written on the hull with a grease pencil.I got it home and put a new battery and spark plugs in it,shot a blast of berryman down the intake and it fired up and sounded good.I then pulled the plugs and di a compression test and sure enough it was low about 120-125.I pulled the fuel filter off and the gas looked funny,really dark,so I siphoned some gas out and it was premix at least 50-1 or so.I siphoned out all the gas and put some fresh gas in .Then I took it out and ran it like I stole it,which basically for what I paid for it .I wore it out for about two hours till it hit reserve,I then rechecked the compression 150 and 150. Apparantly they had been running premix in it the whole time and it had never properly seated the rings,I sold it the next week for $4300.00.I paid $400.00 for it and had to buy a trailer to put it on,so I grossed about $3600.00 on that one.Wish I could buy ten more like that one lol.