I have a 97 gtx. It had not been drove in a year or so when i bought it. Carbs were locked up so i replaced. New batery and cleaned fuel tank and lines...It started up and idled fine. When put in water it was a little sluggish on start then picked up at approx 40mph ...rpms not consistant would increase and decrease....then rpms would lower and engine would stop. It would start right back and the throttle would be a little slughish the get back up to approx 40 or 45 mph the shut down again. It would run for approx 2 to 4 minutes bettwen episodes. any help