On Tue, 23 Nov 2010 17:46:50 +0700, Bruce
wrote:

Out of curiosity, why chain the shaft? Are you running on one engine?
And, if you are how is it working for you. I tried it and it simply
dropped the speed by about half :-(

On our boat we can improve fuel efficiency by about 25% running on a
single engine assuming a speed of no more than about 1.1 SQRT LWL.

We have Detroit 6-71 2-cycle diesels which are not efficient at low
speeds. Running single engine gets operating RPMs up to a normal
level. This is useful on long passages in relatively light winds and
calm seas. If the wind kicks up we need more power to maintain speed
and stability.