They acknowledged that a lot of people thought it was a good idea (I used to do it on two prior boats, before I got a feathering prop with our current boat 12 years ago); however, the internal workings of the transmission really don't like being challenged.

If you are on a boat the doesn't often sail faster than 3 or 4 knots, it probably is less of an issue than a boat which is sailing at 6-8 knots (or faster). The force increases proportionally to the cube (or is raised to the 4th power?)...

Anyway, the technical adviser at Mack said: "Don't do it, unless you really don't care if you're planning on have a transmission rebuild prematurely."