Re: puled thermostat off to check pump oper. lots of salt inside
Much of what shows up in the cooling systems of outboards is not sodium chloride, or sea salt, but calcium and other materials. Frequent flushing with clean fresh water helps to get rid of it. <br /><br />Once it builds up, the best way to clean it is to remove the heads and clean them with straight muriatic acid, available at hardware stores.<br /><br />This is an extremely caustic acid and should be used with care, but it will remove the build-up. Once removed, you need to neutralize with baking soda and wash thoroughly.<br /><br />Avoid contact with stainless parts and paint. Wear eye protection and keep the baking soda nearby to put on any splashes.<br /><br />Excessive buildup not only restricts the flow of water, but insulates, preventing proper cooling.