How to flush outboard motor cooling system?

Last updated on September 2nd, 2020 at 06:20 pm

The process of flushing an outboard motor cooling system is very important, especially if it has been used on salty waters. It is essential for the engine maintenance, and not doing this might lead to salt blockage. Blockage will result in overheating, which in turn will wear away the insides of the engine. In modern times, there are several easy ways to conduct this flushing, as listed below:-

  • Flushing bags:

Flushing bags are made up of heavy plastic and fully enclose around the lower end of the engine. They are soft sided and are supported by frameworks. It is attached with a garden hose for filling and circulation of water and after that the engine is turned on. Even though the engine is on, there is no extra noise produces. However there are certain aspects to be careful about e.g. the bag must be well fitted and heighted so that it easily fit the engine without any leakage. Moreover there should be no propeller available at the time of installing, and the engine should be on the neutral mode.

Outboard Flushing The Right Way - BoatUS Magazine
  • Already built in flushing attachments:

This is the easiest process and requires no extra hard work. Moreover, this process mostly works without the engine being turned on, which is an added bonus. The garden hose attachment is pre-installed in the engine, all you need to do is attach the hose and turn the water on for 10 minutes. It is completely noiseless. The only characteristics to be careful about are that you should strictly follow the user manual and the connection should not be cross-threaded.

  • Ancient way:

In old times, flush muffs were used to flush outboard motor cooling systems as they are cheap. All you need to do is connect a garden hose, fit muffs on gear case and turn on the water. However a lot of factors have to be taken care of e.g. no additional water intake should be carried out as it leads to overheating. The muffs should be properly secured over the case as they tend to slide away or drop sometimes. Make sure that the engine is pumping water or else it might wear out. The engine speed should be kept at neutral.

Outboard Flushing The Right Way - BoatUS Magazine

Do manufacturer companies require a certain flushing procedure?

There are a large number of companies manufacturing outboard cooling systems. The best ones include Honda, Suzuki and Yamaha. We will mention the methods used to flush the best outboard motors.

  • Honda:

The Honda flushing procedure differs from size to size and model to model. Most of the smaller motors have an optional flushing attachment that enables the process of flushing through a port located near the gear case. Middle sized engine require only the factory wash, which is conducted through the port located on the lower left side of the gear case. Large engines are to be cleaned with the factory wash and a garden hose, without the engine turned on. During all these procedures, the engine must be vertically placed for easy flushing.

  • Suzuki:

Suzuki guides people to either use flush muffs or the built in ports. While using the flush muff, the engine should work at a neutral speed and the water should be flushed off after turning the engine off. However for proper drainage, the engine should be brought back to the original position.

  • Yamaha:

Yamaha allows the usage of all three methods without any restrictions. The engine should be placed vertically, and should be running on a neutral pace. In case of a flushing port, the engine should be turned off. Only cool water needs to be provided for effective flushing.




We don’t spam! Only Important Stuff.

This is William Parker, an RV lover, and an adventurer - in short, Beaver Instincts. I am also a professional content creator who knows fairly well how to compare different products, services, and sites. Announcement: Invest in Our Blog to get up to $20K per month in passive income. Email

Comments are closed.