Mercury 250 Optimax

Hi I have just fitted the above motor to a rib in the UK. It came with a high performance gear box. Is there any difference from a normal 225 opti gear box. Just trying to prop it correctly. Thanks W

You always prop your engine to the recommended RPM's. Which in the case of a 225OPTI, I haventaclue. But google Prop Wizard ,and I'm not talking about Harry Potter,this will give you an idea of the size you need. Then it's trial and error as it will depend on the weight of the RIB,plus load, whatever amount of gear,eg. diving gear,number of bodies,beer,ect. that you load on it.
It'll also depend on whether you use aluminum,stainless steel,three or four blade.
So what you are looking for is a prop that puts you,at WOT, between the Min and Max RPM's for your engine,regardless of high performance gear box.