Hi. I am new to the forum. I just purchased a 31' Mallard Sprinter. It is in nice shape and the engine sound good. There is one thing that I am not sure of. After I run it a few miles, 2 or 3, the engine sounds like it is running away. The tackometer doesn't change but it is really noisy. Then in a little bit it sounds normal again. Is this normal or do I have a problem?