I did a Barnacle Buster recirculating flush a few years ago. Works great and something you should do every once and a while. What I've been doing ever year at the time I winterize the boat, is to soak the raw water system with a product called "Acid Magic", about $20 a gallon. Acid Magic is a buffered phosphoric solution used to clean pool systems. Much less toxic than muriatic acid and easy on the skin. I just mix up a 10:1 solution in a 6 gallon jerry can, pour it into the top of the strainer (no issues with my SMX pump's impeller), and let it sit for a couple of hours. If you're doing a recirculating flush, you probably want to go with a stronger 4:1 solution. Flush with another 6 gallons of water and a box of baking soda to neutralize the acid, then another running flush with water for a few minutes. I then fill the RW system with RV antifreeze. That's been keeping my system clean without the hassle of a recirculating flush. I should note that while I cruise and fish in salt water, I moved to a fresh water marina a couple of years ago. Recirculating acid flushes aren't as critical for me as in the past. John Baczek Puffin, NT32 Watch Hill RI