yamaha cuts out need help
 

I have a 2003 15 hp ob on a 12' alum. boat with a 9 pitch prop. The boat
came with a 10.5 pitch prop. At about 1/2 throttle the engine cuts out.
It seems like an electronic problem. However, the seeped of the boat seems
about 20-25mph. Is thier a high rpm cut out?
Any help would be great.
Teri