27 Fuel Saving Tips

[baz]

This is a FYI... and not to be confused with it being specific to R-27, although it does have a nice 'ring' to it. :lol:

Came across this today while idling/doing some boating research... I thought other new Tugnuts might like to see this, and as a reminder for the more seasoned ones... 😉

I liked the "If you are going to run fast, run topless." advice.

http://www.boatingwithdawsons.com/boating-articles/27-fuel-saving-tips.html

 

[JamesTXSD]

Naked Cruising Tuesdays is fun, and you don't have to go far to enjoy the day. 😎

On a more serious note, our experience shows using a fuel flow meter does make a difference in efficiency.

 

[Hydraulicjump]

Hey Barry,

I bet this quote generates a debate among the topless Tugnuts.

"If your boat has diesel power, you paid more in the beginning but you will be saving on the on-going fuel costs over the same gasoline powered vessel. Diesel engines cost less to run than gas and they are most efficient when run at 80% of maximum speed."

Is that 80% of actual speed or 80% RPM at WOT? Is that on plane (presumably) or displacement? And how is efficiency measured?

Just sayin'

Jeff

 

[baz]

Jeff:

Since the the "speed" word is associated with the words "Diesel engines" in the sentence I have to think "speed" relates to the engine's RPMs. Thus for our Yanmar 4BY2-150 engine the 80% would represent 0.8 x 4000 or 3200 rpm.

As to "plane" or "displacement" modes I would assume the sentence refers ONLY to the engine, and that "efficiency" also related to the engine's efficiency and not anything else. Of course planing and displacement at the 80% engine speed/RPM will affect fuel burn.

 

[Levitation]

The diesel engine may run most efficiently at 80% of maximum rated power (or may not, that is for another discussion) but the most MPG in a 27/25 will be around 5.5-6.0 knots and 6 MPG
Now slowing up even more will give a bit more MPG but you might find your SOG going backwards because of wind/current.
6 for me (psychologically) seems to be the sweet spot between getting there and not getting there - that and my innate cheapness. The family surname is Irish but my kids always claimed that dad was scotch.
The incompressible medium that our bow parts when in motion, controls the efficiency equation not the engine.

 

[Todd]

For a Ranger Tug the best fuel saving tip is "SLOW DOWN"

Here is some data from my R29 collected on one afternoon, on the Hudson, slack tide, little wind.

RPM - Kts - MPG
Idle 670 - 3.8 - 11.1
1000 - 5.1 - 8.7
1300 - 6.8 - 8.2
1400 - 6.9 - 6.8
1500 - 7.3 - 5.0
1800 - 8.1 - 4.3
2000 - 8.5 - 3.4
2500 - 8.8 - 2.0 Trimmed 8.9 - 1.9
3000 - 10.5 - 1.4 Trimmed 10.8 - 1.6
3500 - 13.6 - 1.3 Trimmed 15.2 - 1.5
4000 - 16.5 - 1.2 Trimmed 19.3 - 1.4

When you look at the NM per Gal column it is evident that, once in gear, any forward motion of the throttle results is less efficient travel. At idle I could travel 1,650 miles on a single fueling (150 gal, main & reserve). It would however take 18 days, non stop, 24 / 7.

 

[baz]

Todd:

Fuel tank, waste tank, fresh water levels when you made the measurements ?
What kind of load were you carrying onboard ? (Gear and people)
Was your bottom clean ? :lol:
Dinghy on swim step ?

I certainly agree with the "slow down" to minimize fuel burn. In general it also makes for a more comfy ride and less noise.

 

[Todd]

The topic is fuel saving tips. All of the items mentioned in the last post can and will effect fuel economy but I have not found any one item that has as much effect on this as throttle position (read that as speed). In my Car, Truck, Motorcycle, Boat, Airplane, or Rail Car (yes I love my toys) in the long run going slower results in fuel savings.

I do not know the exact configuration of my 29 when I recorded the data. I am not saying anyone else would get the exact results. I am not sure I could get the exact results again. This was data recorded over a 20 minute period of time that will never ever be repeated.

If you do the arithmetic you will note that increasing rpm from 1000 to 4000 increases speed from 5 Kts to 15 Kts but increases fuel burn (Kts / MPG) from .6 gph to 14 gph. Three times the speed, Twenty Three times the fuel.

I will conclude by saying the best fuel saving tip is slow down.

 

[Capt. Wanabe]

While there is much truth in the previous post "the best fuel saving tip is to slow down," for our Ranger boats there is an exception worth noting. The usual relationship between power consumption and velocity in a displacement hull is to the cube root hence the admonition to slow down. There is, however, an area of the power:speed curve that is remarkably linear. I discovered that on the 2012 Desolation Sound cruise while trying to keep up with Andrew. I had fallen behind secondary to a mechanical malady. After Andrew fixed our boat he took off like a rabbit to join with the rest of the fleet. So, while trying to keep up with Andrew, I paid close attention to the actual mileage we were getting. At first I thought I was going to burn through all of my fuel in twenty miles. Not so. From about 8 to about 15 knots the actual MPG is fairly constant running about ~2mpg. (Results may vary depending on the extra load, trim, weather, etc.) That is where the Ranger "semi-displacement hull" properties come into play. So the bottom line is to save fuel go seriously slow (7 knots or less). But if you are going to exceed 9-10 knots you might as well run the rpm's up to 3200 where the diesel reportedly likes to be anyway. 😛 As to the very top end of the curve, you don't want to go there!
Frank

 

[Todd]

I noticed the same results. If you look back at my data you note that between about 2800 and 4000 the speed increases considerably with the MPG staying about the same. For very little increase in fuel you could save a lot of time.

Anybody know the max continuous running RPM for a Ranger 29