I am using less fuel at cruise speed in my 19 footer because I am only turning about 2600 rpm to run 35 or so---maybe 3 gallons per hour.<br /><br />After about 4000 rpm fuel consumption is all the same, I just get there a lot faster with the v8.
My stingray has a 350. I uses a good bit less than the 125 outboard I used to have. I can go out for a two days on the weekend and not use a tank of gas. I've never really tried to monitor it but I would say with normal cruising probably 3 or 4 gallons per hour. More pulling skiers or tubing.
My glastron has a 23 gallon tank and a 4.3liter 190hp v-6. I get my best economy at about 3000-3200rpm. I have driven from suisun bay to stockton through the sloughs and used about 15-16 gal. Thats about 4 gallons per hour on a 4 hour trip at 35 mph. kick it up to 40-42mph and I use almost 20 gallons on the same trip. <br />I can pull skiers around the lake all day for 2 days during an overnighter. I think that fuel economy is not as much about the size of your motor but your driving habits and your power to weight ratio.
I have an old Bertram 20 with a 4.3LX. Boat weights in at about 4,500 lbs. At cruise, about 20 knots, I get about 3.5 nautical miles to the galleon. That's about 4 galleons per 24th of a day.
Go to Barnes and Noble and pick up any one of 4 boating magazines with boat tests. They all list fuel consumption at various rpm/speeds/boat weights/etc.<br /><br />Buy the biggest motor you can afford in the size of boat that fits your needs----trailering down the road is also a consideration.<br /><br />"Standard" power in most I/O configurations off the shelf is not enough, in my opinion. Sea Ray is terrible about this---heavy, well made boat with no power---unless you purchase the upgrades. Every 50 horsepower increase costs roughly a additional $1000.
