well first off you really need to know how many rpms your motors turning before you do anything, once you figure out where shes at rpm wise running how you would normally run with the load (weight ) you normally carry you then can adjust your pitch up or down in order to get the motor where shes running in the upper max rpm range at w.o.t., being its a merc 2 stroke the max rpms are 6000 so i would adjust prop and pitch size trying to get as close to that as i could, typically a ss prop of the same size is going to spin a lil more rpms, i am running a aluminum 13 pitch prop and with an average load i'm hitting about 5300 rpm at w.o.t. so i just ordered and recieved a new power tech 13 pitch ss prop today that i'm hoping should put me a little closer to the 6000 mark