Many thanks to all who replied for all your good avdvice. So on balance it looks like I need to circulate barnacle buster and/or saltaway through the the system from the raw water intake to the exhause elbow. So now the question is, do I do this by running the engine and therefore letting the impellor do the work, or do I use, say, a bulge pump sitting in a big bucket? If the latter then presumably I would need to first remove the impellor to allow the water through?
