A while ago, When priming the fuel filter on my Yanmar 2GM20F I could not get the prime screw to tighten, and when I removed it I found that the threads inside the top housing of the figure had corroded and the female threads came off and were wrapped around the screw. I purchased a new top housing and installed it. A few weeks later I decided to upgrade the primary filter to a Racor 220 from a 110. At the same time I replaced all of the feed hose up to the fuel feed pump. When connecting to the fuel feed pump, the intake feed bolt was loose so I tried to tighten it, and again found that the threads had corroded. In this case I had to replace the entire feed pump. Has anyone had a similar problem? This was not caused by "cranking" on the bolt. I have never heard of this problem before. The engine is 10 years old ( on my '91 Hunter 30) Regards, Doug Margison, SV Mokum II