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How to flush your outboard motors (properly) in 5 easy steps

Updated: Aug 14, 2020

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

ear muffs attached to the water intake on an outboard motor
PICTURED: Ear muffs positioned over the water intake on a Mercury outboard motor

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.

Hose attached to ear muffs on Mercury outboard motor
PICTURED: Hose attached to ear muffs & turned on

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).

Water spouting from the tell tale on a Mercury outboard motor
PICTURED: Water flowing from the tell tale

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.


Do you have a question you want answered? Feel free to submit it via the form below and I'll answer it in depth for you.


Do you need to service your boat? Our team of technicians at Edencraft Marine have over fifty years experience in the industry. We're still yet to come across a problem we can't solve!

Feel free to get in touch via (03) 4216 5411 with any service enquiries.

22,999 views4 comments

4 Yorum

Allen Parton
Allen Parton
09 Haz 2023

Hello, I have a 2019 Suzuki DF9.9B how do I get the fuel out of the fuel hose without running it until it’s dry, or do I need to? The fuel in the line is approximately 2yrs old now, due to covid I couldn’t use the boat so I’d like to drain It. I bought it brand new it’s my first boat and motor? Any advice or info would be great thanks


hello, I just bought a boat with a 1979 Johnson 55 on it and I was wondering if you knew anywhere I could get parts without making me go to the likes of eBay.


Hey Risto74, with Mercury's you can buy an adapter to cover all of the intakes but this might not be the case with Yamaha's. For the larger outboards you're probably safer using the side flush point, but if you were to use the ear muffs method you'd have to block the other two intakes on the lower unit to flush the motor correctly. Hope that helps! Feel free to call on (03) 4216 5411 if you need anymore help


Hi I have a 250 yam 4 stroke fly buy wire have four pick ups if I put it on the muffs the water is very warm the guys at Yamaha told me use the flush point what ate your thoughts as he said muffs don’t supply enough water as there are two more situated lower

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