An Evinrude outboard motor uses a shear pin to protect the propeller from accidental impact. The shear pin will break off when the propeller hits something underwater, such as a rock, tree stump, or other large or heavy object, allowing the driveshaft to keep turning while disengaging the propeller. Shear pins are designed to be readily changed, even out on the water, with either simple tools or no tools at all.
Access the propeller unit on your Evinrude motor. This may mean putting it up on a table, going to the back of the boat on dry land, or tilting the motor upwards and out of the water so that the propeller is exposed.
Remove the cottar pin that holds the propeller nut in place. Some Evinrude motor propeller nuts are held on by a cottar pin, in which case the shanks of the pin need to be bent straight with pliers so that the cottar pin can be pulled straight out.
Remove the propeller nut with an adjustable wrench or pliers, whichever works best.
Pull the propeller off once the nut has been removed. Take note of the hole in the driveshaft that is roughly 3/4s of the way up. This is where the shear pin is installed and replaced. If the shear pin has broken off inside of the hole, push on it firmly until it falls out.
Coat a new shear pin with grease, if necessary, and slide it into the shear pin driveshaft hole.
Replace the propeller and push it onto the driveshaft, lining the pin up with the recess that it will fit into. Turn the propeller on the driveshaft while pushing it onto the shear pin. The turning motion will come to an abrupt halt when it is seated correctly.
Replace the nut and the cottar pin, if applicable, making sure to bend the cottar pin shanks to lock it in place.
Shearing off a propeller pin can happen at any time. It is always best to keep several available in your boat along with pliers, so you will be able to replace one at any time, on or out of the water.