Fawlty Towers economics

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I find that my boat is most economical at WOT (From an MPG perspective). She's an S23 with a KAD32. I cruise at around 3200RPM, but for distance covered, she's most economical at WOT (3800RPM)

Anyone else in the same boat as me? (no pun intended)

PS. I am not including displacement speed cruising (which doesn't exist in my world, except when passing other boats/on rivers/coming into harbour)
 
gjgm said:
that seems very odd.Are you sure WOT is giving highest gallons per mile, not miles per gallon!
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:p I was thinking that myself for a while! Yup, i'm certain. GPM is what I burn when using friends boats :p

I get around 1nm per 1litre of diesel at WOT which I find very affordable. I did 50nm last weekend (at WOT as I was travelling alone and meeting people at destination, so needed to keep myself happy!) and burned 54 litres. Happy days!! And to think I want to upgrade... if I kept this boat i'd never have to even think about fuel consumption
 
alt said:
I find that my boat is most economical at WOT (From an MPG perspective). She's an S23 with a KAD32. I cruise at around 3200RPM, but for distance covered, she's most economical at WOT (3800RPM)

Anyone else in the same boat as me? (no pun intended)

PS. I am not including displacement speed cruising (which doesn't exist in my world, except when passing other boats/on rivers/coming into harbour)
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Not quite the same but a similar situation with my boat - SD hull, and obviously most economical at displacement speed, but fast cruising speed at 2250 rpm using 5GPH on each engine giving 12 knots Vs WOT 2400 rpm 7GPH each engine giving 16 knots means it is the same cost per mile. I believe this is due to the hull being more 'on the plane' at the higher speed and therefore more efficient. - Also creates less wake, so less upset barges ;)
 
BGW said:
Not quite the same but a similar situation with my boat - SD hull, and obviously most economical at displacement speed, but fast cruising speed at 2250 rpm using 5GPH on each engine giving 12 knots Vs WOT 2400 rpm 7GPH each engine giving 16 knots means it is the same cost per mile. I believe this is due to the hull being more 'on the plane' at the higher speed and therefore more efficient. - Also creates less wake, so less upset barges ;)
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Never realised you were capable of 16 knots - fancy bringing me wakeboarding if you're at the next CPB meet at Dromineer? :p
 
alt said:
Never realised you were capable of 16 knots - fancy bringing me wakeboarding if you're at the next CPB meet at Dromineer? :p
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It has been known.... - Richard (Reflection) has had his son wakeboarding behind his cruiser.

Unfortunately, my wife, having finished filing her nails, decided to file one of our props on a rock and bent the shaft in the process.

Had an emergency lift done to straighten them as much as possible, but still more vibration than I would like above displacement speed, so it will have to wait until next year after the remedial work on this winters lift out.

Will definitely be at the meeting.
 
generally reflects an overloaded boat relative to power with planing hull

whilst the engine economy is reducing over the last 10% of revs (big generalisation) the additional power is delivering speed that's enabling the hull to deliver even bigger savings though reduced drag

unlikely at over 30knts when drive system drag will become a bigger factor still

easy to load those boats up over time - time for a locker clear out?
 
It obviously depends on the boat, but Volvo's own figures for a KAD32 show the most economical speeds to be below 3200rpm.

I.E. not much point in slowing down to save fuel if you are already doing less than 3200rpm.

I recently did 60nm and 130litres in bouncy conditions. That figure might have been 120litres in calmer water. Average rpm was 2800-3000, surfing down the waves.
 
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