Thanks for all the suggestions!!! Just to be clear, there is minimum to no growth in the sea chest itself. The growth (and blockage) is below the seacock. When I do clean this I have to open the seacock and scrub below the ball valve to open it up. After it opens up seawater refills the sea chest and I have to shut it off to avoid overflow when it is unclogged and the cover is removed. Now, I know why the previous owner kept a toilet brush in the engine room.
Just a quick question, is it okay to run the engine while the cover is off the sea chest while I am trying to run BB through the raw water systems?
It's all Good