Doug King: Most of us like to look after our boats. We polish them, wash them, change the oil, have them serviced regularly. But what about the cooling system? It's often overlooked, and over time, salt, dirt, sand, mud, can build up and block the cooling system and restrict the flow of cooling water. Flushing the cooling system on a regular basis will ensure proper operation of proper temperatures, and give you longer engine life.
There are two ways to flush outboard engines, the earmuff method and the built-in method. The way to use the earmuffs are to make sure that they're put onto the cooling intake firmly, and there's no leaks. Plug the hose in, turn the water on. Wait till you have a good water flow, then start the outboard engine and check that the water is flowing through the cooling system by having a look at the outlet. After two or three minutes, turn the engine off. Turn the hose off. Remove the earmuffs, and the engine has been flushed with fresh water.
With the built-in system, engines may have a connector where you connect a hose straight to the engine. The advantage of this is that you can flush the engine while the boat's in the water, or you can use it where you're not allowed to start the engine and make noise. To use this method, you just plug the hose into the connector, turn the water on, leave it on for two or three minutes. The upper unit of the engine will be flushed. Then turn the hose off, re-secure the connection on the engine, and the engine is flushed.
The key points for flushing engines are, don't flush your engine unattended. Always monitor the flushing process. Check that your cooling intake screens are clear, and always check the telltale, to make sure that the water is circulating through the cooling system. Flushing your engine, particularly after you have been operating in saltwater, dirty water, or silty conditions, will ensure that your cooling system is kept clean, and you'll get a longer life and better operating temperature out of your engine.