Yanmar GM engines are common and reliable, but one weakness on the raw- water-cooled version is the exhaust elbow, where seawater is forced into the elbow at the engine manifold, writes Ian Pirrie.
Problems occur when hot exhaust gases are mixed with seawater: this is a very corrosive mixture. The elbow has a concentric tube welded inside the outer tube, which forms a water-cooled jacket around the exhaust passage: this weld is very prone to failure. Read More
