I noticed about 2 months ago that my boat is topping out about 64 mph, sometimes even at 60 mph. This spring it would run 72mph. Only thing I have had done to it between those times is, I had the water pump and impeller replaced. It still comes out of the hole like I am being shot out of a cannon. The prop (fury 25p) is a little dinged but it was that way when it was running 72. I am going to have it worked on in a few weeks at Propeller Dynamics. Runs fine throughout the rest of the throttle range. Just stops gaining any oomph beyond 60mph. 90 percent throttle 60mph. 100 percent throttle. still 60 mph or so. only turning 5000 to 5300 rpms. in va, temps are below 50 for most of these runs, when I first noticed it was in Nov and it was about 65 degrees out that day. the motor does make a singing sound nnnnnNNNNnnnnnnNNNNnnnnnnNNNN instead of a constant sound. That is the only thing I have noticed that is different. Any clues? I just bought new fuel line and a new bulb yesterday, but I have not replaced them yet. I forgot, I did have the ignition switched replaced a few weeks before I noticed the drop in speed. I don't normally run the boat much over 60 so I don't know if this started before or after the switch was replaced, but I don't think it would be a contributing factor in the loss of top end.