If you saw our 2 Most Common Outboard Engine Issues: Fuel Systems and Flushing video, you got a peek at the salt build-up, scaling, and corrosion that can form inside of an outboard that isn’t freshwater flushed on a regular basis. It’s ugly. In fact, the engine we showed as an example was just six seasons old, yet needed thousands of dollars in repairs. But you can prevent this kind of harm, as long as you know how to flush an outboard properly—and you give your motor a flush after each and every saltwater use. Here’s the basic routine.

How to Flush Outboard Engines that have a Flushing Port:

  1. Remove the cap from the flushing port, and thread your garden hose into it.

  2. If the boat is in the water, tilt the engine up until the outdrive has drained of saltwater.

  3. Turn on the water, and let it run for at least five minutes.

  4. Do not start the engine.

  5. Remove the hose, and replace the cap.

How to Flush Outboards that do not have a Flushing Port:

  1. Attach a pair of earmuffs to the hose.

  2. Slide the earmuffs over the lower unit, so they fully cover the engine’s water intakes.

  3. Turn on the water, and make sure it’s flowing around both sides of the lower unit water intakes.

  4. Start the outboard, and make sure water is coming out of the tell-tale.

  5. Let the engine run for at least five minutes.

  6. Turn the engine off, then turn off the water and remove the earmuffs.

Watch our How to Flush an Outboard Engine video, to see the process from start to finish and learn a few more tips about flushing your outboard engine.



Some large, high-dollar boats have semi-custom flushing systems built right in. To see an example of how these work on a triple-engine Intrepid 430, watch our Intrepid 430 Sport Yacht Outboard Engine Flush video.


What about freshwater boaters? They don’t need to worry about this stuff, right? Wrong! Freshwater lakes and rivers may not be as corrosive as saltwater, but they certainly aren’t free of contaminants. And freshwater boaters are just as likely as any other to suck sand, grit, or tiny particles into the engine intakes. So while flushing after each and every trip isn’t quite as imperative, they should still give their engines a flush every few trips and/or after they run aground, or run through shallow waters with a sandy bottom.

Freshwater flushing is one of the most important maintenance tasks of owning an outboard engine, but it certainly isn’t the only one. Visit our Maintenance section to learn about things like how to keep your outboard engine looking like newhow to change engine oil on a 4-stroke outboard enginehow to change the lower unit oilwinter storage tips for outboard motors, and more.

Written by: Lenny Rudow
With over two decades of experience in marine journalism, Lenny Rudow has contributed to publications including YachtWorld, boats.com, Boating Magazine, Marlin Magazine, Boating World, Saltwater Sportsman, Texas Fish & Game, and many others. Lenny is a graduate of the Westlawn School of Yacht Design, and he has won numerous BWI and OWAA writing awards.