Engine Flushing - 101

I am often asked; "How often should an outboard engine be flushed and what is the best location to flush from?"

The engine should be flushed after each trip with the engine running and preferably from the lower unit water intakes.

Using the garden hose with the engine running and flush muffs on the intakes, the flow of water is through the water pump, up the pickup tube, and allows time for the water to warm up, releasing salt and mineral deposits from the powerhead and exhausting it out of the engine.

This process is critical for engine longevity and will reduce costly repairs in the future. The salt/mineral builds up each time the motor is used and these microscopic deposits build on each other and can become so powerfully destructive it can push motor mounts forward causing shifting issues and premature gear case failure. This same buildup is what gets into and clogs passages that will restrict flow causing overheats and excessive engine cylinder temperatures.

The flush port on the front, side or back of the engine is the second location - not preferred - but is acceptable and should be used if the lower unit water pickup port is not an option. A boat in a sling over the water is definitely one of the applications where this method is the only choice.

The hose should be connected and water turned on, engine started and allowed to run for five minutes. The water flow from the average household faucet is 45 psi and at this pressure there is not much time for the powerhead to heat the water up and discharge the mineral content; however some heat is better than no heat. The example I use to explain the benefit of heat is comparing two salt solutions that have dried on a counter top. Hot water will dissolve the deposit faster than cold and most of the time cold will not release it all unless left to soak or scrubbed off.

Using the flush port located at the powerhead forces water down the pickup tube to the pump instead of through the pump. It will still clean sand and salt, but is not as effective due to direction of flow.

Salt Away and Salt Terminator are good release agents and are a definite help when they can be used.

An ounce of prevention is worth a pound of cure and, in this case, maybe more. Prevention is also more trouble-free time on the water.

Have a great and safe summer,

Chris Mapp

Coastal Bend Marine
Port O'Connor, TX
361 983 4841