Have Boat Questions? Ask a Boat Repair Expert.
Hi, my name is Kerry
A 15x17" prop is a typical size for a large outboard motor or a small block inboard.
The larger is probably the right size.
The correct size is the size that allows the engines to rev up to their rated maximum RPM at wide open throttle.
If the engine revs past it's rated maximum RPM, the prop is too small.