4500 rpms is all shes do

[menacer]

If the motor is tuned and all else fails try down sizing from the 15 inch prop, it may be too much . Try a 14 1/4 x 17 prop and see if your rpms come up. That should get you over 5000. One other thing may be the motor is too low in the water. Make sure your cavitation plate is even with the keel of you hull before you switch props.
Dennis