I spoke to the Yamaha factory rep yesterday at the NY boat show regarding the corrosion of the exaust manifolds. He did admit there has been some problems but not widspread. He said to flush the motors often. Most problems have been saltwater motors but there have been some that came from freshwater. I asked what should I look out for. He said to check the oil after every use and if you see any water in the oil discountinue use. He also said that if a problem exists you may see an oil sheen in the water around the lower unit. To inspect he said to look up the shaft with lower unit off with a narrow bean flashlight and there is a flat square plate that should have 90 degree edges. This plate should be intact with defined edges. If the plate is worn and the edges are not sharp and you see dark spots of corrosion that will be a sign that the corrosion is a problem. He said if I had any problems to bring the boat to a Yamaha certified dealer and have them call their customer service number. He said they have been helping with repairs but the amount has varried due to warranty, usage and care.