A friend of mine has something like the larger of those Katadyn pumps, but bigger. He acquired it without having to pay for it, but as far as I know, he has never found a use for it. Even that Katadyn 35 is going to be bulky, and it produces only 4.5 litres per hour! If you reckon that everyone is going to want at least 1.5 litres a day, that is a lot of pumping! If that is the plan, I would have to say that a different plan is required! Even as a back up, it does not seem a good idea on cost vs practicality.
There is a bit of a write up about the devices here:
http://www.portablewaterfilters.org...katadyn-powersurvivor-40e-desalinator-review/
Interestingly the author comments on the manual model too and reckons it is going to be hard work as a sole water source.
Stopping in on shore locations and filling water storage containers seems a more workable idea.