Whats the average mpg on a 20hp 4stroke outboard

[boater1234]

Can't seem to get a clear answer online about how many MPG a 20hp 4stroke outboard would get at wot.I want to run a 6 gallon tank and i'm trying to fig out what i would average for a full tank.Also will a 20hp efi really get alot better milage then the carbed 4stroke?

 

[JB]

Re: Whats the average mpg on a 20hp 4stroke outboard

Outboards don't get mpg, boater, they get gph (gallons per hour). You would get much less GPH if it were on a 16' tinny than on a 'toon.

I would expect an EFI 4 stroke to do better than a carbed 4 stroke, but I couldn't predict anything without putting it on my boat and measuring performance and fuel efficiency for that particular combination operated according to my preference.

 

[boater1234]

Re: Whats the average mpg on a 20hp 4stroke outboard

Got ya.I was just wondering what i would get for a 6 gallon tank on average.I should say how many miles i could travel up and down my coast, i guess i will just have to play around with the motor and just run it to see what i get for total miles on a 6 gallon tank,I'm not sure if i want to go with a 6 or 9 gallon tank thats why i'm asking.I fig the amount of spots i hit in one day would be close to 50 miles round trip.I go up and down the whole gulf coast in my area for reds,snook and trout.

 

[foodfisher]

Re: Whats the average mpg on a 20hp 4stroke outboard

Plan 1/3 up, 1/3 back, 1/3 just in case.

 

[JimS123]

Re: Whats the average mpg on a 20hp 4stroke outboard

I was curious about the answer myself, and I realize that any forum data would likely be "opinion" only, so I googled manufacturer's web sites and did the math myself. Looks like about 6.6 gal for your specified trip. Had I guessed I would have said 4.5-5.0 gal, so even with a guess a 6 tank would be inadequate. When you said "WOT" you automatically rulled out the 6.

 

[blackhawk180]

Re: Whats the average mpg on a 20hp 4stroke outboard

Knowing I'm treading on scared ground, I choose to display MPG and GPH on my Lowrance HDS 7, and find that MPG is most useful adjusting trim/RPM because that is what's important to me. At $4/gal, how far can I go before I have to refill the tank? My Merc 115 4 stroke burns between 4.8 and 11.2 GPH on plane. So where do I run it to get the most mileage out of my tank? Turns out, about 6.2 GPH gives me the most MPG (4.8) at about 30 MPH. My MPG drops to 3.1 at WOT which is not worth the extra 8 MPH to me. Which way is better? Not interested an argument about which way is better or proper but I'm staying with MPG.
I suspect if my dad had a GPS and digital fuel flow monitor, he would have chosen MPG but sadly, I can't ask him any longer.
As for your 20hp 4 stroke, I guess I'd just fill the tank, run it full bore for an hour and refill the tank. That will at least give you your GPH at WOT. If you have GPS for speed, you could crank the math and get your MPG but that would only be accurate for WOT and as you can see from my example, I get way better MPG at a lower speed.

 

[emilsr]

Re: Whats the average mpg on a 20hp 4stroke outboard

The general rule of thumb is divide the horsepower by 10 and that'll be how many gallons you burn at WOT every hour. In this case that number comes up to 2 gallons/hour, or 3 hours per tank. This is just a general, easy to calculate in your head kind of rule though.

The more accurate answer is a properly tuned 4-stroke gasoline engine will burn 0.5 lbs/hr at WOT. In your case, 20hp x 0.5 lbs = 10 lbs/hr. Gas is 6.1 lbs/gallon, so 10 lbs / 6.1 = 1.64 gallons/hr....or a little more than 3.5 hours on a 6 gallon tank.

MPG will be dependent upon the speed of the boat. Try planning your trips in hours (versus miles) and that'll help with the math.

 

[boater1234]

Re: Whats the average mpg on a 20hp 4stroke outboard

All great info,now i just have to decide which motor i want,lol.

 

[foodfisher]

Re: Whats the average mpg on a 20hp 4stroke outboard

That's cool, a no motor boater. You wouldn't be a "small boat lover" in another life would you?

 

[simplystressed]

Re: Whats the average mpg on a 20hp 4stroke outboard

how heavy of boat is this going on? I like the idea of efi but the displacement of yammy or merc is where I am leaning. don't imagine either is hard on fuel

 

[sutor623]

Re: Whats the average mpg on a 20hp 4stroke outboard

Id carry either two 6 gallon tanks or a 6 and a 3 if I were in coastal waters. I like two tanks no matter how much gas I carry, just makes me feel more comfortable.

 

[boater1234]

Re: Whats the average mpg on a 20hp 4stroke outboard

Boat is only 190lb flat bottom 1436 lowe rated for a 20HP.

 

[simplystressed]

Re: Whats the average mpg on a 20hp 4stroke outboard

Boat is only 190lb flat bottom 1436 lowe rated for a 20HP.

in that case I would be looking at the suzi but don't think there is a bad choice between the brands you are considering. still can't imagine gph would be much different efi vs carb in that small a motor?

 

[boater1234]

Re: Whats the average mpg on a 20hp 4stroke outboard

From all the youtube videos i have seen on the suzuki,most being the 15hp efi,it has a ton of power for a little motor,plus i'm going with the 20hp instead of the 15hp so i will have more hp and power to play with.On an inflatable boat the 15hp planned 4 full adults and went a suprising 33kmph which in mph is 20.5mph,thats pretty impressive with 4 people in the boat if you ask me.I'm only going to have 2 people and gear so my boat will probally fly.He also tested the boat with 1,2,3,and 4 people in the boat with the standard 10 pitch prop
1 person was 38kph=24mph / 1 person was 40kph=25mph
2 people was 36kph=22mph / 2 people was 38kph = 24mph
3 people was 34kph=21mph / 3 people was 35kph= 22ish mph
4 people was 33kph=20.5mph / 4 people was close to 35kph=22ishmph

THIS WAS ALL WITH A 10PITCH PROP / THIS WAS ALL WITH A 11PITCH PROP
ALSO ALL WAS DONE WITH A 15HP 4STROKE SUZUKI EFI,SO I WOULD THINK A 20HP WOULD GET A BIT BETTER RESULTS