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Single v/s Twins : Fuel consumption ?

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Old 11-08-2007, 09:14 PM
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I would guess that a 32 fountain with twin SBC, instead of twin BBC, would be far more fuel efficient. I need tons of tab in typical Pacific conditions, and tabs down really burns fuel. Get that weight out of the aft end, and less tabs, so less fuel burn.
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Old 11-08-2007, 09:33 PM
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I have yet to see a boat test for a twin engine boat that had peak mileage much over 2 mpg. I have seen a number of boat tests with singles that got peak mileage of over 3 mpg. Small blocks or big blocks, the results were similar. You just can't push two drives through the water, and expect to get great mileage. When you add an extra engine, you are adding over 1000 pounds to the boat, so that contributes to even more drag.

I will add that some sort of cobbled up rich running carbureted big block single isn't going to do well for mileage either. Go EFI, and have it properly tuned.

Michael
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Old 11-08-2007, 10:45 PM
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Quote:
Originally Posted by Michael1 View Post
I have yet to see a boat test for a twin engine boat that had peak mileage much over 2 mpg. I have seen a number of boat tests with singles that got peak mileage of over 3 mpg. Small blocks or big blocks, the results were similar. Go EFI, and have it properly tuned.
Boat tests..... they do a lot of long distance trips calculating fuel mileage during those

My experiences with twin 5.7L SBC fuel consumption were real and calculated; 12 years of ownership with many trips on 3 of the Great Lakes, trips on the Atlantic, and a LOT of trips up and down the Mississippi River using GPS for mileage traveled and calculated by top-offs during or end of the trip. Fuel consumption on the 242 was verified (and VERY close- I give them a lot of credit and would buy again) by FloScan.

EFI and roller valve trains have made the SBC even more effcient, and they are incredibly reliable.

With gas prices the way the are now, and since I'd only consider a twin, the performance boat I would consider would be in the 28-32' range with a 350 MagMPI/ Bravo package. I've noticed a few Fountains, a 28' PowerPlay, and some Formulas as well that would make great boats without breaking the bank on fuel. We sometimes could go 2-3weekends without putting fuel in the tank!

You have to realize and accept one thing with a boat equipped this way; you won't be the fastest out there. You can still get good cruise #'s though- 50+ mph at 3400 rpm with either boat we owned.
With the fact that AT, Fountain, Saber, Pantera, Formula, etc. have flashy offerings in 28-32' with twin SBC, the cool factor is still there with four pipes out the back and two keys to turn at the dock (and one engine to get you back to safety if something goes wrong the other).
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Old 11-09-2007, 12:33 PM
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Boat tests..... they do a lot of long distance trips calculating fuel mileage during those

My experiences with twin 5.7L SBC fuel consumption were real and calculated; 12 years of ownership with many trips on 3 of the Great Lakes, trips on the Atlantic, and a LOT of trips up and down the Mississippi River using GPS for mileage traveled and calculated by top-offs during or end of the trip. Fuel consumption on the 242 was verified (and VERY close- I give them a lot of credit and would buy again) by FloScan.

EFI and roller valve trains have made the SBC even more effcient, and they are incredibly reliable.

With gas prices the way the are now, and since I'd only consider a twin, the performance boat I would consider would be in the 28-32' range with a 350 MagMPI/ Bravo package. I've noticed a few Fountains, a 28' PowerPlay, and some Formulas as well that would make great boats without breaking the bank on fuel. We sometimes could go 2-3weekends without putting fuel in the tank!

You have to realize and accept one thing with a boat equipped this way; you won't be the fastest out there. You can still get good cruise #'s though- 50+ mph at 3400 rpm with either boat we owned.
With the fact that AT, Fountain, Saber, Pantera, Formula, etc. have flashy offerings in 28-32' with twin SBC, the cool factor is still there with four pipes out the back and two keys to turn at the dock (and one engine to get you back to safety if something goes wrong the other).
I'm sorry. I'm not following your logic here on why a boat test where fuel consumption is measured at various fixed speeds, and allows for a direct comparison under similar conditions between boats, is a worse measure of fuel consumption than your aggregated trip conditions with varying speeds, load, water condition, and a sample size of two boats and two fuel mileages, neither of which had a single engine. The poster asked how the mileage would be with a single vs. a twin. You'll never get those twins to 3 mpg unless you replace them with diesels.

Michael

Last edited by Michael1; 11-09-2007 at 12:43 PM.
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Old 11-09-2007, 12:58 PM
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My 28' with 600hp gets 2mpg average with a combination of cruising, no wake and a few minutes of WOT, a buddies 29 twin gets about 1.2-1.3 under similar conditions.

One run I make regularly is 10 miles down river and 20 miles of bay with 3 miles of no-wake in clear lake area, 66 miles round trip and usually 33 gallons.

Last edited by Wobble; 11-09-2007 at 01:01 PM.
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Old 11-09-2007, 01:33 PM
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Just for reference, my 7500+lb 292 with twin 6.2 MPI's get 1.6-2.0 mpg at 45-50 mph (SmartCraft SC5000). Really depends if I am going up or down river!
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