A boat motor, like any motor, needs to be used regularly to prevent seizing the motor and problems with starting and running. In the off season be sure to drain the motor and store in a dry, moisture free area. It is also important to store outboard motors out of the water if left on the boat over the summer.
Larger boats will typically have a permanently fixed inboard motor. Usually these motors are diesel and are started with a switch and a key, similar to a vehicle. Any motor should have a kill switch which can allow you to immediately stop the motor if there is any type of emergency or someone is knocked overboard.