Vortec 5.7 Gas milage?

[lord1234]

How much gas usage should I expect? Can't find any results on the internet

 

[Scott Danforth]

0.4# of fuel per HP commanded per hour

A gallon of gas in the US is 6.82#/gallon

Beyond that, would need to know is your boat 4' long or 40' long, are you in rough water, calm water. Clean boat or dirty coat, with or without wind, at displacement speed, or WOT at 50mph.....and the 50 ither variables

If you are worried about fuel economy, buy a sail boat or a row boat, if it has a motor, it will burn fuel.

You will burn between 0.5 and 2.0 gallons per mile

 

[lord1234]

I'm just going to start messaging you directly with my questions LOL

25' boat, and its the Gulf...you live here, you should know what it's like...

 

[Scott Danforth]

I will not answer messages. That is what the open forums are for

You missed the fact I answered your question. BSFC is .4#/HP/hr

So completely tied to the HP you command.

 

[lord1234]

So...with a 250hp motor, .4*250 = 100 pounds of fuel per hour, 100/6.82 = 14.66 or ~15 gallons an hour? So with an 80 gallon tanks(thats what I got), I should plan for 1.5hours max runtime out following the rule of thirds?

 

[H20Rat]

Isn't gas closer to .5#/hp? Diesel is .4

In any case OP, that only tells you if you are going to flog your engine by holding it wide open for the entire time. Fuel consumption is NOT linear with throttle. Best cruise MPG varies with load and the hull, but it is usually above planing speed by a certain amount but never at WOT.

The only way you will get an accurate answer is to install a fuel flow meter that has GPS. Or if you want a swag, find a similar boat on boattest and compare.

 

[harringtondav]

Fuel consumption varies based on how much engine power you use (how you operate) per Scott's data above. Hole shots guzzle gas, WOT operation guzzles gas. Just on-plane cruising guzzles less gas. Boats use a lot of fuel.

Reference point: My boating pal, me in my boat and our families took a long river cruise. Mostly 32-35 MPH cruising. My 4.3 got 4 MPG. His 350 mag in a 20.5' got 3 MPG. Boats are thirsty.

 

[Tassie 1]

Boats are thirsty.

I've got two 5.7 315 hp MPI's, in a 30 ft fb cruiser,
So twice the smiles per nautical mile...or knot

Those smiles are priceless too

 

[harringtondav]

I've got two 5.7 315 hp MPI's, in a 30 ft fb cruiser,
So twice the smiles per nautical mile...or knot

Those smiles are priceless too

When your fuel consumption is measured in GPM, your boat is a big 'un. My pal has a 42' Bluewater Coastal Cruiser. Twin Cruisers 350. He putts along at 1600 rpm to the swimming hole and anchors for the day. His GPH is pretty good for a big boat.

 

[Scott Danforth]

Isn't gas closer to .5#/hp? Diesel is .4

BSFC for diesels are about .333 (range is .300 to .35). I must have stared at about 40,000 fuel curves on Cummins, JD and Cat diesels over the past 25 years. 2-stroke outboards are .5#/HP/hr

 

[Scott Danforth]

So...with a 250hp motor, .4*250 = 100 pounds of fuel per hour, 100/6.82 = 14.66 or ~15 gallons an hour? So with an 80 gallon tanks(thats what I got), I should plan for 1.5hours max runtime out following the rule of thirds?

if you are commanding 250hp. remember, your 250hp at the prop is closer to 270 at the flywheel

since the load varies, the power needed/commanded varies, and the fuel consumption varies.

your two best economy spots will be at idle (usually about 5-7 knots) and just above planing speed. however that point varies from hull to hull and motor to motor (need a fuel flow meter to identify it)

my experience with an 80 gallon tank in my 26 foot boat when I had the SBC in it was about half a tank over a full day of boating/anchoring/etc in the gulf between Tampa and Sarasota and usually covered about 65-85 miles. best run I have ever done was 120miles with light cruise bar-hopping in door county Wisconsin going around the DC Peninsula on a light chop day. the multiple stops and starts where what limited me there.

when I re-launch here in a few weeks with the new thirsty big-block, I will be using the new fuel flow meter to adjust for best cruise fuel burn for long trips..... and to see if I can burn more than 3 gallons per smile at WOT......

 

[harringtondav]

BSFC for diesels are about .333 (range is .300 to .35). I must have stared at about 40,000 fuel curves on Cummins, JD and Cat diesels over the past 25 years. 2-stroke outboards are .5#/HP/hr

I'm retired JD. They spent a lot of time and $$ getting their diesels compliant with EPA Tier 4. ...also had to redesign the machines to find a place to squeeze in the charge air cooler, elaborate EGR, ATD, DEF tank, etc.

From your data have these modifications hurt fuel economy on big diesels?

I understand RR locos and towboat giant diesels must now comply.

 

[Scott Danforth]

I'm retired JD. They spent a lot of time and $$ getting their diesels compliant with EPA Tier 4. ...also had to redesign the machines to find a place to squeeze in the charge air cooler, elaborate EGR, ATD, DEF tank, etc.

From your data have these modifications hurt fuel economy on big diesels?

I understand RR locos and towboat giant diesels must now comply.

Locomotives needed to meet an aggregate average. Back in 2008, i designed locomotive engine pods with Tier 3 QSK19 motors. Since the new diesels were so much cleaner than the T0 EMDs, most fleets only needed to convert 40% to the new motors in the traditional non-attainment areas of LA basin and Texas. T4 did drop fuel economy over T3 because of the fuel dumped into the exhaust during regen.

 

[harringtondav]

Locomotives needed to meet an aggregate average. Since the new diesels were so much cleaner than the T0 EMDs, most fleets only needed to convert 40% to the new motors in the traditional non-attainment areas of LA basin and Texas.

I worked for the ICGRR '74-'79. EMD GP16s...it think. Amazingly simple, and dirty. Two cycle. Exhaust valves in the heads, scavenge ports in the charged air box. Four traction motor axles. Easy to rebuild. Disconnect the con rod basket, and pull the cyl/piston/rod assembly out. I still see a few around. I bet these put a drag on the "aggregate average".

 

[jimmbo]

My 5.7 will burn 130 liters(35 US Gal) in about 90 minutes at WOT, but will cover more than 150 km(90 miles)

 

[mr 88]

I'm just going to start messaging you directly with my questions LOL

25' boat, and its the Gulf...you live here, you should know what it's like...

What kind of 25 ' boat ? CC / open bow ,DC , WA speed type ,Express cruiser ,Cudy Cabin ? Beam ? Weight. I/O or straight inboard ? How many in your crew when out and about ? Is she propped correctly so that at wot your just under your max rated rpm ? What type of prop are you running ? What's the condition of your bottom . Generally, your best mpg at cruise puts you in the 2900 -3100 rpm range and you may get 1.5 to 2.8 depending on all the variables listed here and on the other replies.

 

[QBhoy]

Mine will do 20 litres an hour at cruising mid to late 20’s and 2300ish rpm. Will indicate 80 litres per hour at wot at about or just over 5000 rpm and mid to late 60’s. Mpi though. Not a carb.

 

[lord1234]

What kind of 25 ' boat ? CC / open bow ,DC , WA speed type ,Express cruiser ,Cudy Cabin ? Beam ? Weight. I/O or straight inboard ? How many in your crew when out and about ? Is she propped correctly so that at wot your just under your max rated rpm ? What type of prop are you running ? What's the condition of your bottom . Generally, your best mpg at cruise puts you in the 2900 -3100 rpm range and you may get 1.5 to 2.8 depending on all the variables listed here and on the other replies.

When you say 1.5->2.8 is that "gallons per hour"?

25' Cuddy cabin. 4500 dry weight, but lets assume 6500 full weight(or 7k).(this covers all people on the boat and gear etc)
IO with volvo penta outdrive
Lets assume correct propped
Prop: Stainless steel 14.5-19
Bottom is in great condition

 

[Scott Danforth]

see post #11, however since you have a single prop, expect to get a little less efficiency vs a DP

 

[mr 88]

When you say 1.5->2.8 is that "gallons per hour"?

25' Cuddy cabin. 4500 dry weight, but lets assume 6500 full weight(or 7k).(this covers all people on the boat and gear etc)
IO with volvo penta outdrive
Lets assume correct propped
Prop: Stainless steel 14.5-19
Bottom is in great condition

No that's MPG .