Cole, We own a 1986 GB 42 Classic with twin Cat 3208 N's, naturally-aspirated, 210 HP. At +/- 1500 rpm, speed is 8.5 knots, I estimate 5 to 5.5 GPH. At 2000 rpm, 10 knots, 10 GPH. This is non-scientific, no FloScan, etc. The Cats are great, low-stress, trouble free. But, they are WIDE, and, if you prefer to cruise 8.5 - 9 knots, I think that 120 HP ford-Lehmans might make more sense. Many late-model GB's have high HP engines, up to 435 HP, IMHO GB's are extremely inefficient bots at over 10 knots, and it makes more sense to look at a different vessel rather than trying to make a slow boat go fast at astonomical fuel consumption rates. Just my opinion. :-) Regards, Scott Gordon Starstream GB 42-944