We just bought a 1997 Seadoo XP Jetski we have it out a few times and it started and ran however it would just simple quit on us.. We would get it started back up then rolled in the water several times but flipped it back over quickly.. Since then we changed the plugs added a new battery and cleaned the fuel filter because we were having trouble getting to start... Now after starting it the plugs immediately foul.. Any ideas what could be going on?