Jim,
I have very recent experience w/ Marsolve. I simply closed the seacock, removed the in-flow hose and inserted into a bucket of 1:1 solution (water and marsolve). I ran the engine until I saw marsolve coming out of the
exhaust pipe, shut the engine down and waited 2 hours. I then re-hooked the in-flow to the seacock, opened it up and started the engine. I went from virtually no water to over 3 gallons / minute. I am one happy sailor, and best of all it only cost $25.00.
happy sailing, GG Charleston,SC