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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Fuel Consumption
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Thread: Fuel Consumption Reply to Thread
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Topic Review (Newest First)
12-25-2011 12:46 PM
travlineasy
Quote:
Originally Posted by LakeSuperiorGeezer View Post
If engine runs lean, could burn exhaust valves. I would leave as is.
Just about everyone I know that uses an A4 also uses a product called Marvel Mystery Oil, which is a top-cylinder lubricant that has been around for more than a half-century. It pretty much prevents valve burning, while at the same time aid in seating and sealing the valve and valve seals. You can still buy this product in most automotive stores and it is added to both the fuel and crankcase. I'm convinced that this product alone is responsible for keeping most A4s in good running condition, and at the same time helps boost fuel economy.

Cheers,

Gary
12-25-2011 12:07 PM
LakeSuperiorGeezer
Lean running engine

Quote:
Originally Posted by SkywalkerII View Post
Moyer Marine sent out an email not long ago about a nice little upgrade for our beloved Atomic 4s. How about a new carburetor jet that reduces fuel consumption to 1/2 to 2/3 a gallon per hour! I haven't had the chance to follow up on this yet, but I'm looking forward to it.
If engine runs lean, could burn exhaust valves. I would leave as is.
12-25-2011 08:46 AM
SkywalkerII Moyer Marine sent out an email not long ago about a nice little upgrade for our beloved Atomic 4s. How about a new carburetor jet that reduces fuel consumption to 1/2 to 2/3 a gallon per hour! I haven't had the chance to follow up on this yet, but I'm looking forward to it.
12-24-2011 11:29 PM
joethecobbler 32' boat w/a 4ft draft full keel 10' beem 35 hp. kubota 4cyl w/ a hurth 125 2.73to1 ratio w/ a 19r11 three blade prop. gross weight 13-14000# burning less than 1/2 gal. an hour on flat water.

I think there are alot of factors that will influence the amount of fuel usage beyond just the engine size and operating speed.
even the "freshness " of the bottom job would effect it.
12-24-2011 06:17 PM
JimsCAL I agree that Boasun's SFC estimate of 0.6 lb/hp-hr is a bit high. I would estimate something like 0.45 to 0.50 is closer. But the big thing to keep in mind is that you are typically running at FAR less than rated power. Power requirements vary approximately with the cube for a displacement hull. So reduce the speed by 20% and you cut the power (and fuel consumption) by half (0.8x0.8x0.8=0.512).
12-24-2011 03:59 PM
addict My fuel gauge is an old batten. I normally watch my hours and start checking around 20-25 hours which is about half a tank. My old 2gm burns around 1.25-1.3 liters per hour @ 2400-2600 rpm.
12-24-2011 03:36 PM
Rockter I use a dipstick, with a volume conversion chart.
I don't have a fuel guage.
12-23-2011 07:15 AM
tommays I run my A4 at 1500 RPM as it just stuffs the stern at more RPM to go a tiny bit faster while i have not done exact it is way under 1 GPH

To go from 5.5 to 6.5 knots most likely doubles the fuel burn as thats the point were it stuffs the stern with a 24' W/L
12-23-2011 01:14 AM
jrd22 We have a fuel gauge that reads for both tanks and both tanks have sight tubes (I use these more often than the gauge) and I track all fuel and hours just because I'm anal about not running out of fuel (tanks hold 190 US gal), which will probably guarantee that I'll run out at some point:-)) Our old Volvo 62 hp consistently burns 1 gph at 2500 rpm which is a little over 6 knots through the water when calm. Wide open I"m sure it would use 3-4 gph.
12-23-2011 12:18 AM
Cruiser2B
Quote:
Originally Posted by travlineasy View Post
30-HP gasoline engine, 12,500-pound Morgan 33 O.I., slack tide running at 2,000 RPM, speed of 6.5 to 7.2 depending on bottom cleanliness, 1/2- GPH. This translates to 13 MPG, which I consider excellent fuel economy for this craft.

And, I always keep the fuel tank topped off. Condensation cannot form inside a tank that has no air inside.

Cheers,

Gary
I have gas A4 and use about 1gallon an hour !. I usually cruise at 18-2000 rpm at 5.5knt. I love the little engine as it is quiet and reliable and freshly rebuilt...but it is a gas hog! We had a good sailing season and used about 25 gallons total. I will someday either have a beta diesel or electric conversion....
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