I have a 1999 115 J115PLEEM SN G04559600. I had it out for the 1st time last week. It started fine idled fine and i left the dock. Ran at low RPM to the mouth of the harbor and opened it up. It jumped up on plane and ran great for about 1-2 minutes then it died to 2400 RPM. After awhile it jumped again for about 5 minutes and died to 2400 again. When i got home I changed plugs, fuel filter(under carb cover and put in 20 gallons fresh gas. Yesterday, same results as before. Any suggestions?