My boat just sips the gas, probably used about 10 gallons for 65 miles. Doesn't make any sense to have all that power without using much fuel.
Actually I was on 'E' for the last 15 miles probably, but usually I have 10 gallons or more left when I hit 'E'. My gauge never goes above 3/4, stays on 3/4 for quite a while, then goes from 3/4 to 1/4 in about a mile, then will go to 'E' with at least 10 gallons left. I have never run out of gas, but have never taken more than 20 gallons to fill, and I have a 27 gallon tank. I figure if the tough guys like Shawn, Jeff, & Tim can keep going, I can as well. They drive harder than I do. I didn't refuel yet, so I will have to report back the true usage after that.
I am only getting about 4500 - 4600 rpms out of my newly rebuilt 460. I used to get about 4800 - 4900. Not sure quite what that means, or what might be holding it back. Perhaps Red or other with advanced engine smarts have an idea on that. The timing is set for about 36 or 37 degrees at full advance. When my engine builder was out with me a few weeks ago to get things dialed in, I know he set the timing based on the dyno specs where the most HP was being produced. When he and I were out though it was really rough so I never really went full throttle with it to see the max rpm's. When I held it wide open on Saturday for a while, it was getting 4500 to 4600 only. The max speed I hit on Greg's GPS was 58.3 (with a full tank of fuel and not exactly glass conditions). I used to get about that with my old motor, so I would expect some additional speed with my new HP, given my drive system has not changed at all. Max dyno HP was 391 at 37 degree advance (@ 4700 rpm's). Torque was at 491 at 3300 rpm's.
At rebuild time, motor (460) went from the std 320 hp to about 390hp (as measured on the dyno). Went from 8 to 1 compression, to 9.5 to 1. Different pistons were used. Went to a different cam that is better suited to the power band of a jet boat. Holley 650 was just rebuilt, and I just switched to the HEI distributor from the original points dist. I never actually checked speed via GPS before, but when my speedo was working, I was always in the 58 to 59 range with the pre-rebuilt motor, & same drive setup. The old 460 was tired - only producing about 90 to 105 psi compression. Now all of the cylinders are in the 150 range I think. I am running premium fuel as well, with the old 8 to 1 motor I was running regular UL 87.
Original specs / testing on the CVX20 had it pegged at about 59 mph from the factory with the std setup.
So I still need some fine tuning, but not sure what. Ideas? I does have instant power, and lot's of it - that's for sure.
Saturday was a lot of fun. I liked running alone, nobody telling me what to do and what not to do (LOL). Nobody telling me how fast NOT to go either. It was like having my own big jet ski, and not getting wet. Nice to be on the river with no weeds, as opposed to Mtka a couple weeks ago where I would have to get my wife or kids in the water to clean out the intake each time we ended up in a weed patch (that you didn't even see until you were in it).
The 'Cove' down by Treasure Island was a lot of fun as well.