A carbed 454/330 is about 25gph, the carbed 502's are about 33gph, this is stock. #'s straight from the manufacturer. I have no numbers on blue motors. I hate gallons/hour, why not use standard mile/gallon, though I suppose this would make people use division...challenging I know. Obviously a boat traveling twice as fast using the same amount of fuel is more efficient.

Not comparing our go fast boats to a Grand Banks that does 2.5 gal/hr, or comparing a Hatteras that goes .5 miles per gallon.

So,you're telling that a 502 carbed engine only burns 33 gal/hr compared to a EFI engine @WOT!

Fountain 29 Fever Test Result Highlights
Top speed for the Fountain 29 Fever is 76.0 mph (122.3 kph), burning 39.8 gallons per hour (gph) or 150.64 liters per hour (lph).

Best cruise for the Fountain 29 Fever is 30.2 mph (48.6 kph), and the boat gets 2.86 miles per gallon (mpg) or 1.22 kilometers per liter (kpl), giving the boat a cruising range of 361 miles (580.97 kilometers).

Tested power is 1 x 500-hp MerCruiser 500 MAG EFI.

Hook up a fuel floscan to that 502 and see what real time test show.

i cruised from cleveland to marblehead 60 miles 1 way ,around 60mph at 3500rpm. got a little over 2 mpg with twin 502 mag efi's. 28ft pantera. same boat with a 650hp 548 single got 1mpg and cruised at 60 @ 4700 rpm. twins really cut down on prop slip and really become more efficient than ya think.

2 1/2 hours? Tim Brown deserves some sort of award.

Michael

I have a flow meter on my boat, it reads just over 40, built to 540 horsepower. The stock 502 read just about 34. I'm looking at the paperwork that came with my boat and those are the #'s they quoted (they have fuel flow in 500rpm increments) Obviously a 500hp 502 will burn a lot more than a 502 415, so I'm not sure what you are saying.

Saying all BBC's burn 40 gallon per hour is a bit silly that's all.

I happen to think gallons/hour is useless. I don't know what a grand banks is and I have no idea what you are talking about with reference to the first thought between boats....the boat with the highest mpg is the most efficient, if that's what you are saying I agree with you. Just because it uses less gallons per hour, does NOT make it more efficient.

Unless you are going or a 3-hour tour, and it doens't matter how far you actually go

There you have it .Agree on the efficiency part.

I have a single 32 and it can be a real handful around the docks, especially if it is windy outside. A twin gets you on plane faster, and splits the work between two engines and drives, hopefully giving them a longer life. Double the routine maintenance is actually pretty cheap. My sinle 32 w/502 gets about 1.75 mpg.

he said "no problem... cooler is full and i got plenty of cigars.. throw me a rope"

That's a boater right there...

This thread may go on forever...

But it's fun, so here's another wrinkle. When Mercury introduced the 525SC, a boat magazine did a test of two 29 Fountains, one with twin 260 HP small blocks, one with the single. All I remember is the single engine boat went 10 mph faster. It was 1000 lbs lighter and had less gearcase drag. That's where efficiency comes from. Of course running a blower engine rich will mess that up in a hurry.

At some point a single prop doesn't have enough blade area to do the job. Maybe that's when you have to use two props/drives/engines. Or a Bravo III...