Going the distance..........
 

What kind of distance/ mileage will I get out of my 65 gal. gas tank with a 454 mag running 3500-4000 RPM?

Thanks,
RJ

Someone posted this on one of the boating sites. May have been here on OSO.

http://www.boat-fuel-economy.com/mer...ion-us-gallons

Not even close to correct...ran a poker run for 4 hours at 80% at 4000rpm or better with 7 people burned a little over a 1/4 of a tank. Oh, and running 70mph at 4000.

Tantrums only hold 65 gallons?

you must be spinning 32 props 70 @ 4000

About 4 hrs of run time at 3500rpm. with that motor you might be doing 40 mph so 160 miles or less roughly...

when i had my new tank built a couple of months ago the math showed 69 gallons

I would bet you are going to safely get 2mpg so 130 or so miles.

You are correct.

What hp you making and top speed with the 32s, labbed or stock.

Labbed, 500hp, 83 with six people and 3/4 fuel. :boat:

What are you running? Mine was born with 415hp/ 502's and bravo drives. Previous owner bumped the engines (dynoed at 497) and swapped drives with XR's.

I also have labbed 30's that I run. playing with the setup. For some reason the xr's have a 1/2" spacer that I had removed once, ran a poker run with 5 people. No change in getting out of the hole, the boat ran flatter but 3 mph less. But the rooster it shot was unbelievable. that was with the 32's. Never got to try the 30's like this because the mechanic misunderstood my directions and put the spacers back in. I want to try spinning the props in with and without the spacers.

mine are making 550 hp i run 30s at 5500 87-90 mph depending on the load the boat when i first got it with stock 500hps went 85-86 on gps what rpms you running with the 32s.
.

[QUOTE=rssteiny;3969792]mine are making 550 hp i run 30s at 5500 87-90 mph depending on the load the boat when i first got it with stock 500hps went 85-86 on gps what rpms you running with the 32s.
.[/QUOT

Right at 5000. Your speeds are good to know, hoping to add the Ateco kits to mine this winter, was hoping to see 90's

Actually those numbers are very close. Your numbers are way off, unless you have a 740 gallon tank. :)

A 500EFI burns about 23 gph at 4000 rpm. 23 x 2 engines = 46 x 4 hours = 184 gallons.

:bsflag:...Well then I guess I must've been towed in and don't recall, since I only hold 142 gallons. Thanks for the equation Einstein, but it doesn't work for my boat.

I wasn't trying to be a dik, but math doesn't lie. Do you realize that the numbers you posted equal 7.8 mpg and your boat goes 1120 miles at 70 mph? Now, that is :bsflag:

x2

70 mph X 4 hours=280 miles covered. 1/4 of 142= 35 gallons, 280 miles divided by 35 gallons= 8 miles per gallon OR 4 hours of cruising with a total use of 35 gallons would be 8.75 gallons per hour for BOTH motors or 4.375 gallons per hour per motor to cruise at 70 mph,
So that would mean your boat cruises at 70 mph while using 4.375 gallons per hour for each motor, 1136 miles on 1 tank of gas!!!! You could drive from tip florida to Virginia on 1 tank of gas, you have a unique boat, Smitty

To OP, my Baja with stock 502mpi got between 1.8 to 3.2 mpg depending on cruise speed, babying it at 3000-3200 it would go about 150-180 gps miles on 90 gallon tank and use about 70-80 gallons to fill, (about 3.5-5 hours of run time when not running it hard on small water cruising) fwiw, Smitty

:party-smiley-004:

I appreciate your effort into figuring out how much I burn. I stated that I burned a little over a 1/4 of a tank (perhaps I should have been more specific, as it read on my guage), I actually don't recall how many gallons it took the next time I filled up (I fill up everytime). I have two 72 gallon tanks, and I can guarantee I did not exceed 35 gallons a side (I'm being generous). I'm not saying that my boat is a Prius. My point was the calculation is incorrect. According to the calculation link, My old 18,500lb cruiser would burn the same amount of fuel as my AT.

The numbers on the link provided are very accurate. A 496/502 HO burns about 20-21 GPH at 4000 rpm and 33-35 GPH at wide-open. Mags will burn slightly less.

Soooo....you're saying a 2000lbs 23' boat with a single 496 will burn the same amount of fuel (per engine) as a 9000lb 38' with twin 496's. That makes no sense. If that were true, than, in the auto world, a mustang with a 302 would burn the same amount as an F-150 with the same motor.....

To the OP.

In June I ran my single 502 272 from Orange Beach AL to Destin FL and back on +/- 60 gallons. I believe this trip is around 165-180 miles. Cruising between 3500-4000, 45-50 MPH. The math shows right at 2.75 MGP.

My gauge moves much quicker on the "second half" of the tank. So it's kinda a guess (these are round numbers) that 2/3 of a tank on the gauge equals 60 gallons. 90 gallon tank. I didn't log actual mileage either, but you get the idea.

To a certain extent yes they will burn the same, as boats don't have transmissions, axle ratios, tire sizes, etc.

In a small boat the load would be far less if they were "geared" the same. But, obviously they aren't as we prop our boats to be in the desired rpm range. A 2000 lb boat is going to have a much bigger prop on it. So, a 2000 lb boat with a 30 pitch prop will have a similar load as 9000 lb boat with twins running 22 pitch props(I'm just throwing pitch examples out there). Which means they will burn similar fuel amounts. The difference will be in the speeds.

ok yesterday I had the boat out with a full tank (stopped when I hear gurgling from the vent) ran 24.9 miles and fill the boat back up to till I heard gurgling i took 13.86 gallons of fuel. I ran the boat from 4000 rpm to wot (5000 rpm) a few times for minute each (4) So with a 65 gallon tank I can go 116.77 miles approximately

There you go! That's the best way to figure it out for sure. You could probably stretch it another 40 miles or so(if you had to) by cruising at 3500 rpms. It's just not nearly as fun! :)

Who TF runs a 38' boat with 22" props? Or a 23' boat with a 30" prop? Just give in and admit that this makes no sense....

Did you not read my disclaimer that I just through those pitches out as examples? My point was a smaller, lighter boat will be "geared" differently with a larger prop and therefore experience a similar load compared to a larger boat with smaller props, and in turn burn similar amounts of fuel. The difference will be in the speeds. Or in an example of small single vs big twin, even if they have similar props the load is being split between the two engines on the twin. There will be minor differences in gph because of hull efficiencies but nothing major.

Why don't you give in and admit that you're full of chit. I usually leave posts like this alone as I don't really care. But when someone claims their twin 500hp boat gets 8mpg it's so ridiculous that I feel I have to so no one believes him. Then they correct themselves and state they may have been off but they know the burned 70 gallons max on a 280 mile trip. Still full of chit. You seriously expect people to believe that your engines burn less than 9 gph and your boat gets 4 mpg at 4000 rpm?

I was worried about hijacking this thread but the OP put up his own numbers. Which, by the way, add up mathematically.

Here's a great example for the new 502. Baja 26 Outlaw burned 21.3 gph at 4000 rpm doing 49.2mph. A Cobalt 296 burned 22.2 at 4000 rpms doing 37.8mph. Like I said similar loads so similar gph, the difference is in speeds. Now, if they could just figure out how to get more hp and cut the gph in half(and then some) like you did they would be on to something! :rolleyes:

And I'm quite sure you believe these figures would be exactly the same in salt water and fresh water. I'm done going back and forth with you, you believe what you want. I have owned 7 boats, 5 of them with basically the same power. None of them had matching GPH #'s. My 30' scarab burned a lot more fuel than my Active Thunder, my single engine Baja sipped fuel compared to my 36' Cruisers...the scarab,baja and cruisers, all had carbed 454's.

Your single Baja sipped fuel compared to a cruiser because it cruised at lower rpm, and had one engine.

I will believe what the math says. If you want to believe your boat engines burns less than 9gph at 4000 rpms then do so, but don't expect others to believe it.

I have a 33' stepped hull with the newer 502's with cats, from memory, the smartcraft shows between 11.7and upwards of 13.9 GPH per motor at 3500 RPM which will vary based on wind and waves. I'm running 50 MPH on GPS, so being the math wizz that I am, it appears to be about 2 MPG or a little under. Not too bad from what I see, some of the supposedly efficient Center consoles don't do much better running outboards and topping out at 60. They probably aren't anymore efficient at 50 than me! For what it's worth.

must be the magic DDC hull

So did you do the run on one tank of gas or did you have to fuel up? Wish we could have made it out there, maybe next year!

One tank the run was approx 94 miles and a lot of fun. I kept the rpms between 3500 and 4000 with a few wot bursts. Everyone was super nice there and Templton Landings food was outstanding. I have been there a few times for weddings or dinner and the food was ok. One of the waiters explained they have started making everything homemade. It would be nice to have another tantrum in the run as well, next years run is going be Aug. 8th & 9th hope to see you there.

Interesting math - a few years back I hauled a reproduction antique lap strake boat out of Fort Lauderdale on one of the hottest days I ever experienced down there. I figure we evaporated just shy of 5 gallons of fuel/ hr on the trailer running north.

In all honesty - 4.4 g/hr burn seems more indicative of a mid size O/B at 4000rpm

I have same said 33 with modified 525's and the majic DDC hull... I have fuel flow meters hooked to Garmin chart plotter. It gets 1.8-1.9 mpg cruising anywhere from 40-60 reliably. Then slides down to 1.4 mpg wide open in the 90s. 5000 rpm is 80 mph and 1.6 mpg. The fuel flow meters are dead on. Its measured fuel flow not derived from the ecu. I have calibrated them by filling the tank and comparing total fuel from Garmin vs fuel taken to top it off.