Subject: When a yacht is sailing, will it go faster if the propeller can freewheel?

When racing yachts sailors tend to lock the propeller in gear because they 
believe that this will be faster than allowing the propeller to freewheel.  I 
myself sail and this has caused many an argument onboard the boat and has now 
degenerated into a war of emails.  We've had views from graduate engineers, 
physicists and mathematicians, an ex-airline pilot and physics teacher as well 
as various sailors.  We've managed to aquire various theories and even an Excel 
graph or two but no-one has managed to conclusively answer the question in an 
easy to understand manner.  You're out last hope!!

Re: When a yacht is sailing, will it go faster if the propeller can freewheel?