Welcome,we will try to figure this out for you.We will need some more help from you.
We need the prop size(under the prop nut or at the base of the blades).We also need your wide open throttle rpm
and gps speed.
A induction tach will do if no tach now.
We need the tach to help determine how well your setup works,what prop may help and to tell the results.
Its important the motor is able to operate close to its max wot rpm rating.Of course you can operate at what ever rpm you like
once established.If you read the stickys at the top of the prop forum it may help understand prop selection better.