thoughts on repowering, smaller not bigger.

[bigbill]

with my 2001 450hp john deeres in a 58yf, 8.6 to 9.0 knots is the sweet spot. that is 1100 rpms, and i am burning total without genset 7.4 gph. if i go to 1200 or higher it goes up a bunch. 1200 rpms is about 9.4 to 9.7 knots, depending on tide, and i am burning 10 gph. ang., slow her down a little bit, and you will save a bunch. bigbill

 

[rsmith]

Locking down one shaft puts a considerable drag on the boat. imposed by the non-turning prop. There have been some past threads that, as I recall, indicate that the drag actually reduces efficiency as opposed to both engines running to push the boat at the same speed through the water.

It would be interesting to do a "mythbusters " on that assumtion. In a single engine aircraft if the engine fails to extend the glide ratio the drill is to pull the prop to coarse pitch and raise the nose to stop the prop from windmilling. The theory is that the windmilling prop is doing work and robbing energy needed to extend the glide (for the uninitiated singles do not have feathering props like twins do) I would expect the same theory holds true for boats. Do sailboats lock their shafts when the engine is off?