JW, thanks for replying to my email about the Torqueshift prop. I am replying to you here because I think there may be others who would like to know it won't work for them either.
I did actually get an answer to my email to Land and Sea in the States and they said the same as you - that it won't work for a slow turning diesel engine. This is because there is not enough centrifugal force. In essence they said their prop is designed to allow sports boats to pull up water skiers easily without losing top-end speed.
Seems a shame that us diesel types can't take advantage of what is obviously a brilliant piece of engineering.
Thanks again, Jeff.