f70 yamaha on 170seaark rx prop questions

[seaark170]

I have tried few props anyone have any advice on pitch and size?
just got a 13 1/4 15 going to try tomorrow.had 13 1/2 17 only got 30mph 5200rpm. im looking to get upper 30s with it is it possible .thanks for any advise

[seaark170]

forgot

both boat and motor are brand new and also after breakin