Thoughts about raw water intake restrictions damaging impellers is a good diagnosis! Good engineering thinking Ray and everyone else. I added a relatively large Groco sea strainer to my M18 because I wanted a metal housing and a clear inspection body. My friends say it would fit a destroyer or maybe a heavy cruiser. However! I know my raw water pump will has a good supply of water at start up. That is if the inlet port isn't completely clogged.