Assuming you have already set your heart on getting a used outboard motor, here are some steps to lead you. Different motors can do different things. One motor can do a little of this and that, but each motor has a reputation for something. Find that "something" and choose the right outboard motor for you.
Buy an outboard motor online, in a magazine or by word of mouth. Look for a motor at Small Outboard Motors. Buy an outboard motor through the Boat Trader magazine or online. Check out community boards near the water. Ask the boat salesmen if they have any used motors. The websites are listed below in Resources.
Choose the two stroke motor. The two stroke motor is lighter and faster. It is also less expensive. Choose the two stroke motor when simply trolling around a quiet lake isn't for you. If you are looking for a quick acceleration, choose the two stroke over the four stroke.
Choose the four stroke motor if you are looking for a cleaner and smoother motor. Choose the four stroke for lakes and rivers since they usually meet the EPA requirements. The four stroke motor is also well suited for trolling. It is not light on the budget, so keep this in mind when buying a used outboard motor.
Determine the size of the shaft of your next outboard motor. Choose either a short shaft, long shaft or extra long shaft. Take the boat out of the water, set it on level ground and measure the shaft length. Measure from the top of the transom (where you clamp the motor) to the bottom of the boat. You should get around 15", 20" or 25". These correspond to short, long or extra long.
Choose a brand. Choose from Chrysler, Evinrude, Sears Gamefisher, Honda, Johnson or other brands. Determine whether you are loyal to one brand or willing to take someone else's opinion. Check out Consumer Reports for outboard motors. Read consumer's reviews on Yahoo Shopping. Look around and ask people what they have and why. When you have the whole picture, choose your next used outboard motor.