Fix No Water Circulation in the Outboard Motor

What to Do When Water Isn’t Circulating Through the Outboard Motor

Outboard motors rely upon simple mechanical systems that push water through the engine in order to maintain temperature and avoid overheating. When water flow through the outboard motor is disrupted or stopped entirely, overheating occurs. Here are top four things boat owners can do when they notice that water is not circulating through the outboard motor:

1) Check the Water Pump Impeller

The water pump impeller is the cause of most water circulation and overheating problems. The impeller is essentially a small, round disc with spinning blades used to move water through the circuit of the outboard motor. When the impeller is broken, it stops the supply of water to the engine and results in overheating. Luckily, water pump impellers are relatively simple to install, but they do fail regularly so it is wise to carry an extra water pump and tools onboard at all times and replace the impeller at least twice a year.

2) Check the Water Intake

Turn the engine off and check for anything, such as weeds or trash, which may be blocking the water intake. If a foreign object is present, remove it and restart the engine after it has returned to normal temperature.

3) Check the Water Output

In most outboard motors, the water output is a small tube-like structure that can easily get blocked. If the output becomes blocked, it will disrupt water flow throughout the entire engine. To check for blockage, run a small, thin segment of wire up the output tube and gently wiggle it side to side to dislodge any debris. The water flow through the output should come in a regular, steady stream that is warm but not hot.

4) Check the Thermostat

Although it is rare for the thermostat on an outboard motor to fail, it does occasionally happen. If it becomes obvious that your thermostat has failed and the engine is not warming enough to maintain a satisfactory starting temperature, replace the thermostat immediately as running the outboard without a functioning thermostat will ruin the powerhead.