It really all comes down to the type of design that you are dealing with. You see, if the design is uniquely designed then you may not be able to replace any components that are not from the original manufacturer. Take Newport Vessels, for example. Even if you wanted to, you could not replace their propeller with one from another brand. It would not be compatible. Again, if the issue is that the current propellers have been damaged beyond repair, then get ahold of the manufacturer.