Nautical
Well-Known Member
Doh! knew we discussed it somewhere, still 38knts is mighty impressive if they can get that from a nearly 18 ton loaded 54 foot boat with 600's. The ABS 47 with same engines and nearly 4 ton lighter officially does 39 knts (although I have had 41 out of our demo), good for them if they can crack that speed. Means also the engines are running around 2700rpm at cruising so below the more uneconomical upper ranges of the engines. Once past the 3000rpm mark D6's really burn the juice we have seen IPS installations V's ABS 47 with same the motors but they burn 50% more fuel for 28 knts cus they have to run harder at 3250 rpm as opposed to 2700 rpm yet are the same length and weight. What appears to happen is once IPS engines run past 3000 rpm to attain highish cruising speeds they start burning fuel at shaftdrive levels.