Originally Posted by jackeen
I know horses for courses what kinda fuel figures are ya getting per kmile.
have placed an order for one
Paul the figures that we quote normally raise an eyebrow and clients querry whether we mean consumption per engine rather than the boat in total. However these figures are based on many years experience with DI and now the ETECs.
When we do get a customer who is still not convinced then we show them our fuel duty claims ...... the best way to assure as if we were using more fuel we would certainly claim the duty !!
Anyhow. ... the figures
on a 10m RHIB with twin 200s (one counter rot), vsl weight with equipment 2200kgs, 12 pax plus 2 crew takes it to approx 3500kgs.
Average sailing is 20% at 75% throttle, 40% mid range and balance low range & tickover. Max speed capable speed 54 knots, average speed over the hour 25 knots thus 25 nm in one hour.
Total consumption = 5 gallons per hour ie. 2.5 galls per engine bearing in mind that that is transporting a total laod of 3500kgs.
Now if we fit 150ies to the same boat cons. is same.
On longer offshore runs cuising at say 35knots consumption increases in total by about 1/2 gall.
We put the light consumption relative to load down to the efficiency of the hull and engines but critically we weigh all components before fitting and strive to achieve correct balance of the vsl. In particular we prefer a static hull to be slightly heavier on the bow (achieved by moving underdeck tanks forward) so that the bow does not rise to quickly/high and you need to increase power and trim to get the bow down ie. let gravity bring the bow down.
Thus I guess the moral is that having the most efficent engine around does not mean it will be efficient unless it is operated efficiently.
We have just fitted two vessels with 250ies and are expecting same figures but will report following tests.