Does any body run a Suzuki DF115 motor on his boat?
What propeller size are your running? Any experience with 4 blade props on this motor?
Suzuki's run an aggresive gearbox reduction ratio so they can swing a much larger prop in terms of diameter.
You need to set your engine up to run a 4 bladed prop, which usually involves moving the engine up by 1-2 holes so check first on your transom if you have where to adjust. 4 bladed props need to run up near the surface to be effective so bear that in mind.
Prop pitch will depend on hull type and boat weight