When I start my motor it will only run just a bit over idol speed for 10-15 minutes until it eventually will get up to full speed. This has happened the past 3 times Ive had the boat out. I thought it might have been bad gas so I got new gas, didnt help. After the initial time getting the motor "warmed up" it works better but still takes time to get up to full speed. It will be running slow then kind of starts surgeing a little bit then starts running fast. Any ideas?