I want to buy a 1980 4HP Evinrude Model E5RCSS and I noticed that the 3-blade propeller is a little lose and has a black rubber (or plastic) conical tip that is pierced by a cotter pin. I find this somewhat unusual simply from the point of view of water flow. Is this common practice? Should it be tight fitting or should it have some play? I appreciate any help. Regards.