Gas consumption/hour?

[delvel]

Any of you have a track record on how much fuel older 50-60's outboards(10-20hp) use per hour when cruising around at max RPM?
Thanks
Delvel

[Helmar]

No but I am really interested in hearing this too.

I still use my 4 cycle Bearcat 55 and I know she just sips fuel.
All that running around I did last year at Mason, was out running most of the day, only used 5 gallons out of a 6 gallon tank. VeryBigSmile

[DMCI]

Anacortes to Rosario on $7.00 worth of fuel in a 22 Tolly.

My Dad had a 22 Tolly Express with a 100 hp Johnson that ate plugs and burned 50/1 fuel mix that we bought from the pump at Cap Sante dock.

Seems it would take about $5.00 to $10.00 worth of fuel for the weekend. We would run Anacortes to Rosario or Deer Harbor which would use 10 to 20 gallons for the 25 mile round trip with some trolling, so I'm guessing three to five gallons per hour at 20 knots.

My brother and I would take that thing out almost every weekend and visit the girls that worked at Deer Harbor. I think moorage was $0.10 a foot with shore power extra (Cord running down the dock.) This memory goes back more than 40 years so I could be all wet on this.

[Guest]

I think 3-5 gph extremely unlikely. Here is a test of 2006 outboards.
http://www.popularmechanics.com/outd...oating/1276841
You don't say what year this happened, but I presume it was back when gas was cheap. By 2006 all the outboard manufacturers had done a lot to improve fuel economy.

Note that the 115 EFI Suzuki is burning 16 gallons per hour at full throttle. A general rule of thumb is that a four stroke engine can produce at best 15 hp for one hour per gallon. For diesel it's 20. For an newer carbureted 2-stroke you would expect 10-12. For an older 2-stroke, a bit worse. Here's a link to test results for a 90 hp carbureted Yamaha on an aluminum skiff:
http://www.yamaha-motor.com/assets/p...1184-ALM-Z.pdf
Yamaha claims 8.9 GPH. And I'm sure that's the best they could ever get.

That 100 hp Evinrude at full throttle, assuming it was in excellent shape, was probably burning at least 10 gallons per hour at full throttle. Probably 2-3 at idle. So 20 gallons could run get you 25 miles at full throttle (12-15 gallons) and leave enough for a couple hours of trolling.

[DMCI]

80% Cruise

Regarding the near new 100 hp outboard on the little Tolly, I was advised not to run it full throttle, but to run it at about 80% to cruise.

Bud Leaf at the time a second cousin and widely experienced skipper told me about that. Seems however, that in the last 25 years we lost a lot of good men.

[bruceb]

My limited knowledge on fuel consumption is from running a 90hp 1964 Johnson V-4 and a 1957 Erude 35hp. The fuel consumption comparison is almost 50 % of the V-4 when I'm running the 2 cyl 35hp.
Sooo, in easy terms, I'd guess that the safe number for fuel planning of the 35 hp is 2- 2 1/2 gph. My "safe" number for the 90hp is 4- 4 1/2 gph, although the real consumption number is 3.5-4.0.
Delvel, if you're running an 18hp motor on what I'm assuming is a 14 foot flat bottom boat, the prop is crucial to your consumption, as well as weight in your boat, amount/size of chop. To be safe I'd plan on your number to be 3 gph until you have results ( as in keeping a log book, and yes I do !) that proves, over time and conditions, to be a number you can trust.....
As you pointed out in an earlier post, running at 80% WOT with an outboard will likely get you the best consumption #s over a distance.
My total #s tend to represent maybe 1/8 of my time idling into/out of marinas/anchorages.
Happy boating !

[McSkagit Tim Jones]

Fuel consumption

Bruce's numbers sound about right. Typical fuel consumption used to be stated in the Johnson and Evinrude brochures. As I recall, a V-75 Johnson would burn 6 gallons per hour, nominal.

Use this formula for computing the fuel consumption on modern high speed turbocharged diesel engines:
0.35 to 0.40 pounds of diesel fuel per horsepower per hour.

Use seven pounds as the nominal weight of a gallon of #2 diesel. At 100 horsepower, my engines each burn six gallons of diesel per hour. At 18 knots it's taking about 200 horsepower total (two engines) or 12 gallons per hour. The boat with half fuel and water on board weighs just 14,000 pounds.

I've been running it slower lately, 16 knots at 2600 rpm. I'm probably going to add an inch of pitch to the propellers to improve fuel economy.

McSkagit

[DMCI]

My Dad's boat was a 37' Canoe Cove (The Canadian Bertram licencee). Boat had twin 6V-53 naturals (220@2750) and a 14' beam.

Cruising speed was 25 Knots at 2450 rpm. Had 24 square wheels and 23 x 26 spares. I recall the gear was 1.5:1. We would get passed by gas jobs, but after about 6 or 7 miles they would slow down. Those boats didn't have the muscle to run long at WOT.

We burned about 1.5 gallons per nautical at cruising speed. We had 400 per side of fuel. Dad's joke was that the range was non-stop to Ketchikan. I took the thing to Princess Louisa on vacation one time and it took about $250 to fuel it up. Didn't require fuel for the rest of the trip. The only weather we had was running the straights to Welcome Passage out of Nanaimo . Got water over the flying bridge when running at speed in a four foot chop.

Friend had a 36 Uniflite in which he installed 3208 (210 @2800) Cat Engines which got similar performance

Those days are gone forever but I will never forget them.

[DMCI]

Oops, repost.