What kind of fuel MPG does a standard "car motor" runabout get? [Archive] - Scream And Fly Powerboat and High Performance Powerboating Discussion Forums

imq707s

06-12-2012, 05:34 PM

My Vegas XT with an old 89' 3.0 Looper sucks down lots of fuel....anywhere from 2-3mpg depending on water conditions and how many people are in the boat. If I can cruise at 50mph or so....it will get 3mpg...if it's rough and I'm on and off the throttle a bunch, it's more like 2mpg.

I have a friend that has a 19ft Fourwinns bowrider with a 4.3 Vortec V6 inboard/out board in it, and if I remember right...it's has a fuel tank of around 34 gallons. That thing will run all weekend, pulling tubers, water skiers, wakeboards...and running all around the lake...and it won't even run through a 1/2 tank of fuel.

I have another friend with a 21ft Cownline with a 5.7 Mercruiser in it, and it seems to do really good on fuel also.

What kind of MPG does a typical 19-21ft bowrider get? Everyone I've ever been in just seems to sip the fuel compared to my 2-stroke Looper. Are 4-strokes really that more efficient, or does my old looper just suck the fuel?

laser380

06-13-2012, 09:51 AM

You are trying to compare oranges to apples. Those inboard/outboards are 4 stroke motors and you are running a 2 stroke. I am sure you know that though. You cant compare them together. Its not your looper that is the problem.....it the method that the motors use to make power.....its just part of the 2 strokes history. They love gas. Just the way it is unless you get a fuel injection 2 stroke....then you can come close to matching a 4 stroker.......:cheers:

1BadAction

06-13-2012, 10:04 AM

I'd rather get 1mpg with a performance outboard than 5mpg in a cookie cutter carmotorboat.

laser380

06-13-2012, 10:10 AM

I'd rather get 1mpg with a performance outboard than 5mpg in a cookie cutter carmotorboat.

:iagree: ROFLMAO.....AAAAAAMEN!!!! I cant agree more. Been there....done that....and when the wife says regal.....we do it again at a whopping 40mph all day......:reddevil::nonod:

pyro

06-13-2012, 11:08 AM

If you're going to compare apples to apples...

I wonder how good of fuel economy you'd get from a 19' Four Winns with a 4.3 at WOT/50mph ;)

WATERWINGS

06-13-2012, 11:13 AM

My stock 2.4's get around 4-1/2 to 5 MPG.....

My modded 2.4 gets around 3 to 3-1/2 MPG.....

(on an 18 foot tunnel)

jag3639

06-13-2012, 11:22 AM

Now are you looking at a Mercury package that is an I/O or a car engine modified for water and has a direct drive shaft and prop. My friend has a Correct Craft direct drive. GM 350CI good for about 50-55 MPH. But consider 300 HP in a two stroke engine there is no comparrison. Two totally different things here. Now in respect of guys running direct drive engines they can be wicked fast. 130+ MPH but about you need 800+ HP to get you there. And it will suck fuel faster than any two stroke made. With a I/O setup you will get a bit more gas but remember it will lack speed in comparision to a 2-stroke Out Board motor.

1BadAction

06-13-2012, 12:15 PM

If you're going to compare apples to apples...

I wonder how good of fuel economy you'd get from a 19' Four Winns with a 4.3 at WOT/50mph ;)

agreed. I'm sure we would all get awesome MPG with our "eggbeaters" if we kept it under 3000rpm and 50mph.

Kind of how the steel bore guys say how nic/chrome bore motors wear out faster than their motors... Hell if I kept my nic motor in a less than 6500rpm hell it would last every bit as long, if not longer. lol.

JohnR

06-13-2012, 12:44 PM

I would say an apples to apples would be more like running a 50mph runabout at 35mph and running a similar hp old school outboard at the same pace. My 18ft bowrider has a 200hp V-8 Chevy, my 21ft Checkmate has a 200hp V-6 carbed OMC. Running the family to the same beach as we always do a few miles from home at around the same 35mph in both I used a lot less fuel with my I/O. Fact is 4 strokes are more fuel efficient than a comparable 2 stroke. Throw an ETEC or XS into the mix and it all goes out the window. Add the price of a $20 bottle of 2 stroke for every 40 or so gallons of fuel and you've added 50 cents a gallon onto your fuel cost.

perfmarine1

06-13-2012, 02:56 PM

Get a bigger prop or get a smaler motor. "What" Or do you like to go fast? People ask me how many gallons a hour my motor uses and when I tell them 28 gal a hour"x2 in the family boat" they go wow. Then I remind them I go 100 miles in that hour. Now sit down,hold on,and shut up!!!!!!

jag3639

06-13-2012, 08:52 PM

I have a friend with a Sanger. Blown w/800HP. Guarantee it would out run most any car today in a quarter mile stretch. Bottom line HP and fuel will only go up, John.

imq707s

06-14-2012, 07:04 AM

Thanks for all of the info guy. I wasn’t really wanting to start a debate on 2-stroke vs 4-stroke…..I was just wanting to know what kind of fuel MPG small runabout gets. I know most 2-strokes are less efficient on fuel, but make more power per CI/CC. I know they are different animals. I know what my Vegas (and other 2-stroke boats) get…….just didn’t have any actual numbers on the small 4-strok runabouts. At cruising speeds are they 5mpg, 10mpg, 12mpg? Just wondering out of curiosity. Thanks! :)

BigJohnson

06-14-2012, 07:20 AM

Took my pontoon boat with 50 hp outboard to the other end of the lake. Burned around 8 gallons in 15 miles wide open for an hour and a half. Took my twin engine cat to the same place several times. Get there in 10 minutes and burned around 8 gallons.

speedman79

06-14-2012, 08:25 AM

Not too many boaters use MPG as a gauge for fuel consumption. GPH (gallons per hour) is used mainly due to the fact that there is no odometer in a boat - but there may be an hour meter. To put it plainly your 3.0 looper would need about twice as much fuel as an imaginary 3.0 four stroke carbed "car motor" - however it would make no where near the same power so it's not a relevant comparison. In a real world comparison as far as power goes - your 3.0 looper vs a 5.7l 350 Chevy would theoretically use a similar amount of fuel if efficiency, load, prop, and RPM were the same - but again they are not. The 350 Chevy will do far better due to a higher efficiency 4 stroke design (not spitting unburned fuel out the exhaust), lower idle, lower RPM range power band, it will throw a bigger wheel (moving the boat further at a lower RPM). My point is all engines run on almost the same amount of fuel per cc of displacement - the fuel consumption difference between each motor will be due to the displacement of the motor, EFI or carb , RPM, prop, and load. A fuel injected 2 stroke outboard will be better on fuel than a carbed outboard motor but will still not compare to a 4 stroke car motor or outboard. All EFI does is fine tuning fuel trim - EFI cannot offset the fact that a 2 stroke has twice as many compression/combustion strokes. Jeez I just re-read this and I don't think it cleared anything up - lol.

speedman79

06-14-2012, 08:31 AM

I'm gonna try again :D - If you feel like your buddies boat uses half the fuel that you use - your probably right. Just be mindful of how often you are cruising @ 4500-5500 rpm and he is at 3500.

imq707s

06-14-2012, 08:36 AM

Took my pontoon boat with 50 hp outboard to the other end of the lake. Burned around 8 gallons in 15 miles wide open for an hour and a half. Took my twin engine cat to the same place several times. Get there in 10 minutes and burned around 8 gallons.

Great info.....to bad you don't have that same info on a small bowrider :)