What approximate fuel consumption gph should I be experiencing with my '77
115hp on an 18' c/c running around on the bay, a fair amount of wide open
throttle?

A good rule of thumb is 10% of HP at full throttle for a carburated two
stroke outboards.

Paul


RB wrote:
What approximate fuel consumption gph should I be experiencing with my '77
115hp on an 18' c/c running around on the bay, a fair amount of wide open
throttle?

Paul wrote:
A good rule of thumb is 10% of HP at full throttle for a carburated two
stroke outboards.

Paul

I'm not sure I understand what you wrote. Does that mean my 2-stroke 250
outboard should be burning 25 gallons per hour at full throttle. That
doesn't sound right. Can you restate your formula in English?

--
Stan

RB wrote:
What approximate fuel consumption gph should I be experiencing with my '77
115hp on an 18' c/c running around on the bay, a fair amount of wide open
throttle?

I'm not sure I understand what you wrote. Does that mean my 2-stroke 250
outboard should be burning 25 gallons per hour at full throttle. That
doesn't sound right. Can you restate your formula in English?

--

Yes, you're correct. The general rule of thumb for a two stroke
carbureted outboards is 10% of horse power per hour at WOT. So a 25 HP
would be 2.5 GPH at WOT. A 115 HP would be 11.5 GPH at WOT. So it
stands to reason a 250 HP would be 25 GPH at WOT. It is just a rule of
thumb not exact. I have also read that another rule of thumb people use
is 1.2 GPH per 10 HP. That calculation is actually a little higher than
the one I use.


Paul

Here is a link to Nissan's site that states the fuel consumption for
their outboards. http://www.nissanmarine.com/tech_talk/gas_mileage.html
Even the four strokes come close to the 10% per HP at WOT.

you can't fudge physics that much. It takes a certain amount of fuel to make
a given amount of power. The example of 100hp burns 10gals per hour is darn
close. Diesels burn less per hour because there is more BTU's per gallon of
fuel(if I remember correctly)?

Mercury's Optimax engines are more fuel efficient because of the direct
injection of fuel.


"Stan (the Man)" wrote in message
...


Paul wrote:
A good rule of thumb is 10% of HP at full throttle for a carburated two
stroke outboards.

Paul

I'm not sure I understand what you wrote. Does that mean my 2-stroke 250
outboard should be burning 25 gallons per hour at full throttle. That
doesn't sound right. Can you restate your formula in English?

--
Stan

RB wrote:
What approximate fuel consumption gph should I be experiencing with my
'77
115hp on an 18' c/c running around on the bay, a fair amount of wide
open
throttle?

On Tue, 29 Aug 2006 21:46:00 -0400, "Lost In Space/Woodchuck"
wrote:

Diesels burn less per hour because there is more BTU's per gallon of
fuel(if I remember correctly)?

More BTUs per gallon, and even more importantly, a higher compression
ratio.

The EFI 4 strokes seem to do a lot better than that 1:10 ratio.
I went for a pretty good ride last weekend. We went from the power
lines on the Estero River to South Seas in Captiva, out Redfish Pass
for a ways and returned on a little less than 12 gallons of gas. That
was 7 hours, about 65-70 miles at 3500-4000 RPM
(60HP merc)

3500-4000 RPM is not WOT. So you would do a little better than 6 GPH.

Paul