How much gas will a 340 use?

[stirus]

I'm contemplating purchasing a 2003 340. What is the rate of gasoline usage? at 'cocktail speed', moderate speed, flat-out?

An example of a day trip for us would be Boston to Gloucester which I understand to be 19 nautical miles. Let's say I take it easy on the way to Gloucester but return at a faster pace. What do you think I'd use in gas for that?

Thanks,
Stephen

 

[Hampton]

At best cruise, you will get about .75 miles per gallon in a 2003 1/2 - Latest model 340. In older models, you may get a little better economy. This will be at about 3400 RPM and 25 mph. This burn rate is about 32 - 34 gph.

I can't remember the exact numbers for slow speed, but it will be about 2 - 4 mpg depending on how slow you are willing to go. Flat out, you will burn a TON of fuel and get about 34 mph. I think it is 30 gph/engine.

 

[mistercomputerman]

I think it is 30 gph/engine.

You mean pair?

 

[pchanson8]

I have always got about .75 mpg. I have V-drives and run tabs down pretty much all the time. I can not remember the exact RPM. I did find a few years ago a guy who had a laptop hooked up and charted it at varying RPM. It will make a difference if the boat has outdrives or v-drives.

 

[northern]

At 6 knots we burn 1 US gallon per knot.
At 8 knots we burn 5 gallons per engine depending on wind.
At 22 knots we burn 50 to 55 GPH total.
We normally go 6 to 8 knots.
If you can not afford the fuel you can not afford the boat.

 

[mistercomputerman]

Obviously, it is not a 340. But, FWIW:

410 Sundancer
2009 8.1L

1/2 fuel
1/2 water

and the props are at the prop shop trying to wring another knot out at 3500.

 

[AKBASSKING]

What is the rate of gasoline usage? Thanks,
Stephen

A lot! (Couldn't resist!):grin:

On my 86 300DB I burn about 28GPH total on step at 3400RPMs

 

[Hampton]

You mean pair?

Oh heck no. 34 mph, 60 gph, .55 mpg - not too bad.

 

[Jeremygavin]

2005 340 with bravo 3s. Cruise @ 3400 rpm at about 32mph depending on the sea and wind. I am at approx 1mpg. I just purchased Hill Marine 4x4 props so hoping for a little improvement this year. We'll see what happens.

 

[dpmulvey]

What engines?

 

[Windjammer]

Calm conditions (no wind or current) 3400 rpm = about 21 kt. 13 gph per engine.
"Cocktail" 1500-1600 rpm = about 2.5 gph per engine.
"Flat Out" - 30 gph per engine.

 

[pchanson8]

I did find a few years ago a guy who had a laptop hooked up and charted it at varying RPM.

FOUND IT!

http://www.boatersed.com/forum/topic.asp?TOPIC_ID=123128

This weekend we did some speed runs at different RPM settings with a computer attached to the engines, which gave us fuel flow. Speeds from GPS. Below find my chart. Bottom has a few barnacles from the salt-water days and some scum from our winter fresh water. Sundancer is a 2001 340 with 454 MPI engines and 3 blade props.
Full fuel ¾ water air temperature 64 water temperature 57.

SEA RAY 340
2001
PERFORMANCE

TWIN 454 MPI

Speeds by GPS
Fuel Flows by computer connected to engines.

RANGE IS 215 GALLONS

RPM MPH GPH MPG RANGE

700 3.9 2.0 1.95 419

1000 6.0 3.6 1.66 358

1200 6.8 4.4 1.55 333

1500 7.9 7.0 1.13 242

2000 12.4

2500 18.6

3000 16.9 24.0 .70 150

3200 20.5 26.6 .77 164

3400 24.1 30.6 .79 168

3500 25.0 31.0 .80 172

3600 26.4 33.4 .79 170

3800 28.0 34.8 .80 172

4000 29.5 38.0 .77 164

4300 32.6 47.6 .68 147

 

[mistercomputerman]

That chart says there is virtually no diff in mpg between 3200 and 4000 rpm although you are burning 8 GPH more at 4000.

Interesting.

 

[Hampton]

That chart says there is virtually no diff in mpg between 3200 and 4000 rpm although you are burning 8 GPH more at 4000.

Interesting.

MPH went up 9. That is common in the heart of the envelope.

 

[Hampton]

2005 340 with bravo 3s. Cruise @ 3400 rpm at about 32mph depending on the sea and wind. I am at approx 1mpg. I just purchased Hill Marine 4x4 props so hoping for a little improvement this year. We'll see what happens.

That's the huge difference with outdrives versus v-drives. Zeus boats (not 340's) share a lot of the same features and efficiencies:
Prop shaft in line with water line
Intake integrated into lower drive unit
Exhaust integrated into lower drive unit
Rudders integrated into lower drive units
Less drag requires less HP which leads to less weight required in engine/drives which leads to more speed/efficiency

 

[Jeremygavin]

That's the huge difference with outdrives versus v-drives. Zeus boats (not 340's) share a lot of the same features and efficiencies:
Prop shaft in line with water line
Intake integrated into lower drive unit
Exhaust integrated into lower drive unit
Rudders integrated into lower drive units
Less drag requires less HP which leads to less weight required in engine/drives which leads to more speed/efficiency

Yes it is a big difference. I am one of the few who prefer an I/O. We rarely stay at the dock so I wanted the better efficiency and speed at cruise to get to where we are going. I also do all my own work so it is nice to have more room in the bilge.

 

[BritLady]

Calm conditions (no wind or current) 3400 rpm = about 21 kt. 13 gph per engine.
"Cocktail" 1500-1600 rpm = about 2.5 gph per engine.
"Flat Out" - 30 gph per engine.

Concur :thumbsup:,we get about the same.