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OT- WAG on gas consumption comparing two CC outboard boats

Milacron

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Assume both 4 stroke modern outboards (2007 or newer), both center console with hardtops

1 24 foot Everglades (I.e. Top of the line and heavy w, deep V hull) with twin 200 HP Suzuki OB's

2. 22 foot Sea Hunt or Sailfish ( I.e.moderate quality and weight w/ deep V hull with one 200 HP Yamaha OB

So, at 30 knots, slack tide, slack wind...is the Everglades going to suck waaaaaaaaay more gas than the Sea Hunt ? How much more...3 times as much ?
 
As a standard for estimating outboards is gallons per hour at wide open throttle.

Take one 200hp outboard engine knock the last zero off and that is your estimated gallons per hour per engine, so about 20 gallons per hour at W.O.T.
two 200hp OB = 40 gallons per hour at W.O.T
 
As a standard for estimating outboards is gallons per hour at wide open throttle.

Take one 200hp outboard engine knock the last zero off and that is your estimated gallons per hour per engine, so about 20 gallons per hour at W.O.T.
two 200hp OB = 40 gallons per hour at W.O.T
First off I'm not talking WOT, and secondly I'm talking very different weight boats
 
lve never owned a dual OB either but would presume you wouldn't have to run then both but would want to for better handling

Wouldn't the duals have steeper pitched props than if you were to run a single? No need to
run them at unnecesary high revs.. Say each boat takes 150hp to run at 30 knots.. The single
would have to be screaming, where the duals can just be loafing along...

Thinking about it.. Especially being 4 strokes, If both boats are comparable-ish as far at power needs,
I bet you could get better "mileage" out of the twins if they are running in a lower rev
range..

Just thinking out loud.. Its a lot more fun than doing that working thing.
 
Outboards are rated gallons per hour at wide open throttle full load at correct rpm, no matter what size boat is.
Your best fuel mileage is about 5/8 to 3/4 throttle no matter what size boat.
A boat is not like a car there is no "crusing" for a power boat. the engine is always at load.
I could put a 200hp on a 15 foot john boat and run it at W.O.T and same engine on your big boat at W.O.T they both would burn the same amount of fuel. This is do to they must be propped to run at correct W.O.T rpm. I would need a much bigger prop then you and would go a lot faster and further, but they both would be loaded to max hp and at at same rpm for a hour. so they both burn same amount of fuel.

With duels never had one but they usually go up in prop size. Good thing with duels is you always have a way home if one fails. there is web site that probably have more exact numbers.

My numbers is just a general rule of thumb for all outboards, some better ones maybe a gal or two per hour more efficient. but it general it gets you in the ball park
 
My brother the mechanic said that in a car or truck the middle size engine will have the best mileage for normal driving. The samllest engine will be running at too high an rpm, inefficient, to make enough power to move the car along. The biggest engine will be running too slow to be efficient and it will have several hundred pounds more weight.
The mid size engine will be just right.
Enough RPM and heat to be in the middle of the power/efficiency equations.
Bill D
 
At 30 knots neither boat is WOT, but the single is probably pushing 3/4 throttle.

My 23' Trophy with a single 150 2-stroke Merc would do about that speed at a little over 3/4 throttle. That was a light boat, but 23 degrees deadrise so it took some power to climb out of the hole. It had a lot of lift in the bow and chines, so it stayed on the step pretty easy. IIRC I was burning about 10gph at cruise.

It was a walkaround, so heavier than an equivalent center console. Hull shape is important. Anything over 21 degrees is considered deep-V, but more deadrise means more boat in the water and less lift, but a softer ride in the chop.

I'd venture a guess, the heavier boat is going to burn about 20% more fuel at the same speed, but the engines are going to be loafing. The twins will have a lot more pitch in the props than the single will.

The best economy will be up on a step, throttle back until just before it falls back into the hole, trim up until it starts to cavitate then tuck back in until it stops.
 
WOT fuel consumption is a bad parameter to use in a comparison such as this.

The answer to your question will be more a function of hull design, boat weight, and actual hull efficiency at planing speeds. You have not given enough information to give an accurate prediction on fuel consumption.

I think the real question you should be asking is how gallons per mile. There is a good chance that the twin setup might actually get equal or better mileage than the single but this depends on how the two boats are actually equipped and propped.

Too be conservative I suspect that you will probably end up at a 25% to 50% fuel consumption penalty on the twins with a much heavier hull. If the Seahunt has an inefficient hull, then you will probably be close to the same.

One thing you didn't mention is the beam width of the two boats. There are tons of examples in the real world in which a technically smaller and lighter boat with less propulsion hp actually gets poorer fuel consumption numbers than a slightly bigger boat with more hp. A lot of this has to do with the hull design and how much actual wetted surface area there is.

I would suggest to try both boats out and do an actual fuel consumption comparison.

I would go for the twins. Assuming that you are wanting to do some offshore fishing, the twins will give you the added security of engine redundancy and the ability to get to shore much quicker when the weather turns than the single.
 
It is pretty common knowledge that most modern 4-stokes burn 10% of their rated horsepower, but the numbers I posted are from a Yamaha Fuel Management system. On my Pursuit with twin F200s I burn roughly 40 gallons per hour WOT at a top speed of 45-47 mph. When I cruise at about 4000 rpm I can maintain a speed of around 30 and my burn rate drops to 14-17 gallons per hour.

I found this info. it don't have hull size but has numbers for duel 200hp

Yamaha - Motorcycles, Snowmobiles, Boats, Outboards, ATVs, WaveRunners, Generators, Motorcycle, Scooters, SxS - America's Most Diverse Powersports Company

here is Yamaha web site lots test data should be able to find what you need for ball park numbers
 
Wah.

At ANY of the fuel-burn rates cited, I am reminded why I took up flying instead...

What y'all burn in just one hour would be enough to carry up to 4 souls around 400 to 800 miles at 100 MPH or so...

Don? How are you at sail handling?

:)
 
Somebody needs to do a test drive of both to settle this
Someone knows the answer from real world experiences over the years but they have yet to show up at this thread. That's what I was hoping for, not armchair calculations.
 
Someone knows the answer from real world experiences over the years but they have yet to show up at this thread. That's what I was hoping for, not armchair calculations.

Interesting topic.

Having no boat knowledge, I would have thought each boat would have some
kind of "constant" number reported, to be used in various calculations.

Sort of a coefficient of drag number per se.
 
I recall seeing probably a 45 foot long ciggarette boat with twin 225', in the florida keys,,, the neighbor said it took 4 gallons to get it to open water... but this was 1980... and thirdhand.
 
Wah.

At ANY of the fuel-burn rates cited, I am reminded why I took up flying instead...

What y'all burn in just one hour would be enough to carry up to 4 souls around 400 to 800 miles at 100 MPH or so...

Don? How are you at sail handling?

:)
You can’t drink beer and catch fish from an airplane
Plus you don’t have to pay 4K a year for an annual on a boat
 








 
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