I have a 1988 yamaha waverunner wr500g. a couple of weeks ago I was at the lake and I decided I was going to get it started before I put it in the water. I didn't have it running to long but i heard a loud pop. I shut it down and put it in the water. I started it again and it ran but but chugged. I replaced the gaskets since i did blow one but it still smokes in the engine compartment. any ideas on what this could be from????