How to run mercury outboard out of water

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.

Flushing your motors is an essential part of boat maintenance. It clears the saltwater & sand from your motor, helping to prevent salt build-ups and corrosion.

Salt build-ups inside your motor are a cancer that cause costly issues down the track and keep you off the water (outboard servicing can be costly...).

A full flushing of the motors must be done after every use, and it’s recommended every six weeks if it’s been sitting in storage.

It's important to run the motors long enough for the thermostat to open, allowing the fresh water to flush the salt from the entire powerhead.

Flushing the motors with the hose plugged into the flush point without running the motors, prevents the thermostat from opening and only partially clears the salt build up from the powerhead.

If you’ve returned home late, or you're in a caravan park where the noise of running the engines is an issue, then this is better than not doing it at all.

But you’ll still need to give it a proper flush as soon as you can.

The easiest way to flush your motors properly is with ear muffs & a hose:

Step One

Attach ear muffs to water intake on the lower unit of outboard

Step Two

Attach hose to ear muffs and turn on. Maintain enough pressure that a bit of water squirts out both sides of the ear muff attachment.

Step Three

Turn outboard motor on to idle and check water is coming out the tell-tale (meaning the water is running through the entire powerhead).

If it’s not, immediately turn the outboard off to prevent overheating (and consult your service technician).

Step Four

Run the motor until water starts running from the thermostat relief. This is usually no more than five minutes.

IMPORTANT: don't walk away from your motor while it's running. If the hose fitting blows, or something else goes wrong you'll need to turn off the motors immediately to prevent damage.

Step Five

Run the motor for an additional five minutes, before turning off the outboard motor and then the hose (in that order!).

And there you have it. A simple job that when done correctly will help your motors stand the test of time.

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