So lets say your out on the water, pulling tubers, and the motor starts to sputter and lose power. You checked your tank and you have plenty of gas, so you can rule that one out. Most likely you have fowled the plugs or have a bad fuel filter. If you don't have a spare aboard, clean the filter element and drain any water. This should at least get you back to the dock. Chances are you left your tank low enough for condensation and water to get into the gas. One way around this is to keep a spare filter on the boat or a full tank of gas if you are storing the boat for longer periods of time. Doing this will minimize the risk of water getting into your tank. Adding a stabilizer is not a bad idea either.

Another typical problem on the water is overheating. Best case scenario, it is just a lack of water flow from mud or weeds to the water intake. Inspect the water intake and clean it out. A loose or split hose can also cause slow water flow as well. Regularly replacing the impeller and checking the condition of its housing can help prevent overheating as well. Even scarring or pitting in the housing can cause a good impeller to not pump water like it should.

What about those times when you turn the key and it wont start. Usually this is the sign of a dead battery, but first check the kill switch. Then make sure the shifter is in the neutral position. If you can hear the starter wanting to engage but can't quite get there, you probably have a low battery charge or poor connection. Which is better than some other things that it could have been. 

Your motor has been running like a champ all day long. Your cruising and you go to get on the throttle but you start to feel a vibration. You hear the motor wind up but you are losing speed. You know it has to be your prop so you stop the motor and check the lower unit only to find 20 pound fishing line wrapped around your prop. Outboards can withstand a bit of line, but if the performance is being affected, do not ignore the problem. Raise the motor, take off the prop, and clean the line from the shaft. Not doing this can result into much bigger problems.

These are only a few problems that you may run into when on the water. Sometimes you can get away with a quick fix to get you back to the launch, other times your not going to be so lucky. The real take away from this article is to be prepared. Anything can happen out there so if you have a handy set of tools, a few extra parts, and a little luck, you can trouble shoot the situation and asses whether or not it is a major problem.