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MPG Chart

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scully

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Does anyone know of a chart that would give a guesstimate how many miles per gallons I should be getting on average with my 2018 21SL with a 115 SHO with strakes? I only have 11.5 hours on the motor but boy it seams to be a pig on gas. Ran 5.5 miles up the river and back twice and took 8 gallons of gas, 3/4 of a mile each way was no wake zone. Does 2.75 miles per gallon sound about right with average load?
 
Did you start with a known full tank, or a tank that read full on gauge?
 
When not in the no wake area I ran little less than full throttle, around 6,000 RPM. First trip just me and the wife with full tank gas, second trip 3 people little less than full tank.


H2GO said:
Here is a rig similar to yours but a 22 foot SSX with twin elipticals. They have a chart showing where the sweet spot is. I don't see your exact model listed. Were you full throttle when not in the no wake zone? Still seems like lousy fuel economy.

https://yamahaoutboards.com/en-us/h.../f115/f115/pb_bnt_22ssx_f115lb_2014-10-28_pnt
Click to expand...
 
Yes I stared with a known full tank of gas. Gas gauge has not work right from day one, fluctuates constantly. I told the marina I bought the boat from, same place I keep it docked. Seams like a common problem. Not sure replacing the sending unit will fix the problem but I told them it needs to be replaced/fixed being new.


SEMPERFI8387 said:
Did you start with a known full tank, or a tank that read full on gauge?
Click to expand...
 
We have different set-ups but my best MPG is around 3.1 @ 3700 RPM. Up around 6000 or more, I'm under 2 MPG. That said, we bought it for its utility and not for its milage. My suggestion would be to make sure you have your engine/prop combination dialed in and then enjoy your river cruises with a full tank of gas when you start out.
 
Great advise. I bought the boat for it's room and smooth ride to take my children and grand children out. Gas consumption note that critical, gas at dock is 3.98 per gallon and I can live with that.
 
I only have a 20hp, but my gauge fluctuates even when I run from idle to full throttle due to change of pitch of the tank. It fluctuates probably a 1/8 tank. I think this is inherent of boats. When I get around an 1/8 I start visually checking it.
 
I'm talking about leaving the dock with a full tank of gas and few miles later I'm practically on 1/2 tank or on E. Sending unit is not working correctly. I've had many nitro bass boats in my days and never a problem with the fuel gauge. If the gas tank was clear I could physically see how much gas I have like my bass boat, turn key gauge reads 1/2" tank, pull out side storage compartment see gas in middle of tank, half tank check.


SEMPERFI8387 said:
I only have a 20hp, but my gauge fluctuates even when I run from idle to full throttle due to change of pitch of the tank. It fluctuates probably a 1/8 tank. I think this is inherent of boats. When I get around an 1/8 I start visually checking it.
Click to expand...
 
You obviously have a untenable situation. I'd contact your dealer immediately. I have a digital fuel gauge that seems to be remarkably accurate.
 
So up and back twice at 5.5 miles means a 22 mile trip for 8 gallons. Assuming your average speed was 22mph that's 8 gallons per hour (GPH) and on the surface that seems bad. However, if you went full throttle for every inch you moved outside of the no wake area that might be good fuel economy!

Fuel economy can vary wildly with boats but as bad as it sounds, 2.5 to 3 miles per gallon isn't that bad for a boat. See if boattest.com did a test on your boat or one similar. Toward the end of the review they'll have fuel burn vs speed vs rpm chart.

A good rule of thumb is to divide your engine's HP by 10 and at wide open throttle (WOT) that will be your gallons per hour. I find it's a little better than that with a 250 hp burning 22 GPH on average. My guess is your boat (at full throttle) burns 10 gallons an hour).
 
Hey you guys........Regardless of MPG or how much gas you burn in an hour or just cruising around the lake or going WOT...........IF THE BOAT NEEDS GAS.......FILL IT UP!!!
 
I saw the title of this thread and the first thing I thought was....I don't want to see the "chart"! especially don't want the Mrs. to see it!
 
More of what has been said. Nautical is correct on burn rate per horsepower used. I have leaned NEVER to trust any sending unit in a tank. I know its not cheap but am running Yamaha Command Link on my 150 and I have found the fuel burn rate to be right on. I know how much fuel I put in and then watch the fuel burn rate at the RPM I am going and calculate from that. I am old school so used to calculating burn over time. I would trust command link or NEMA but never a fuel gauge. Also be aware of where the sending unit is placed as that will have a great effect on a fuel gauge readings depending whether if your bow is up or down when running..
Running wide open or close to 6000 is never efficient and if you have a 115 you can figure on 11.5 GPH at wide open and if the SHO has more than 115 then it will but more than that...
 
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