1QwkSport2.5r

The leading edge of the prop is the thickest part of the blade. The prop must be installed this way. The engine turns counterclockwise, so the prop must be installed such that the thicker edge of the blade faces CCW. So yes, the prop would be installed "backwards" on the engine. You would use a prop washer behind the prop nut to secure it - the prop washer will be large enough diameter to cover the whole area of the hub. Propeller blades are airfoils much like an aircraft wing - without the airfoil working in the proper direction, prop efficiency goes down considerably. If doing it correctly is of any importance, I'd suggest turning your prop around as the other guys outlined and fasten the prop correctly (using a prop washer). You can omit the spinner and use a spinner nut and prop washer as well.

pinky_d_brain

Its difficult to understand we get that
Can you give it a try with the littering or rounded side of the prop facing the front of the boat. We don't mind being proven wrong just give it a shot for us please. The prop will hold fine we do this all the time and its made for this application on planes.
its funny but when you flip the prop over the angle or pich is still in the right direction. The defense is the air foil is now working with you.
If you have already changed it from the pic (#8) no problem

Paulekins

hi all i will give it a go but not this week end as i am picking up a 25ft Fairline Fury from Portsmouth
this will be a 2 year rebuild project

well i do need a rescue boat to retrieve my air boat lol
i am also building an under water ROV just in case it sinks and i need to search the bottom of the lake/sea