hey i just baught a new to me, 1999 yamaha waverunner gp1200. i got it started, and ran it for a abotu 15 minutes on the lake. it seems it idles rough and rides rough until i hit about 3,000 rpms then it smoothes out. and you can hear it sputtering sometimes when going in higher rpms, i dont know if this is bad gas, or plugs, or carb? thsi is my first waverunner so any sugestions i should try? also there was oil in the bottom of the engine compartment after i got it home along with some water. not sure where it came from.