Trying to help a friend with her boat, its a 2001 Bow Rider 21ft. It has the 5.0 EFI Engine and Alpha One Gen II? Outdrive. The boat starts and idles fine, gets up on plane (a little slow in my opinion with 1 person) and then just flattens out at about 27-28 MPH. The tach says around 4800 RPM...