I might have mentioned to Ferman and a few others that I had a friend twith a 200 Yamaha 4-stroke that flushed his motor religiously. Literally after every outing it is lift kept and the hose would go on it for 10 minutes while we cleaned up, it was the ritual. That motor developed a leak thru the block due to corrosion. He never did the thermostats and he had a significant buildup of corrosion in and around the t-stats.. Someone else mentioned that there are more sacrificial anodes in the block somewhere that need to be changed. I know that adds up $$$ and even worse to discover a four year old motor that has major corrosion issues, despite flushing.. He patched the holes, drilled one and tapped it to put in a pipe plug and he epoxied the other leak. I would like to think that it is not a common occurrence? BS I looked it up. My Mercs have never corroded like that, Johnrudes either. Just saying... Last couple outings I witnessed multiple Yamaha powered boats on the rope of shame. They all breakdown. My Mercs weakness is in the compressor setup. Lower units too, maybe self-inflicted there. I am hard on the Merc, so if there is going to be a stress related failure I intend to find it..
I'll behave now.