| Fuel
consumption and range values for motoryachts
With
sample measurements on a Grand Banks 36 MY trawler
Data source: Powerboat & Motoryacht Magazine
Evaluation: Yusuf Civelekoglu
Introduction
We
all know, we all hear, that consumption, range, noise and
engine wear are strongly related to the engine revolutions.
The data below show that these relations are beyond the imagination
of most of us.
All
what has been done is that a boat was run with varying engine
revolutions and consumption, speed and noise were recorded.
Data
Table [1]
| Revs
(1/min) |
Speed
(sm/h,knot) |
Consumption
per time unit (l/h) |
Way
made good per unit fuel (sm/l) |
Range
(1000sm) |
Noise
(dB) |
| 1.000 |
6,3 |
7,6 |
1,0 |
1,31 |
73 |
| 1.250 |
7,5 |
11,4 |
0,8 |
1,03 |
73 |
| 1.500 |
8,3 |
22,7 |
0,4 |
0,58 |
74 |
| 1.750 |
9,2 |
30,3 |
0,3 |
0,48 |
75 |
| 2.000 |
9,8 |
40,2 |
0,3 |
0,38 |
77 |
| 2.250 |
10,7 |
53,0 |
0,2 |
0,32 |
78 |
| 2.500 |
14,3 |
68,9 |
0,2 |
0,32 |
79 |
| 2.650 |
15,7 |
84,9 |
0,2 |
0,29 |
80 |
Graphical
Presentation
Comments
As
can be seen in the graphics,
1. Speed of the vessel is the variable least depending on
engine revs. When the engine revs are 1000-1 speed is 6.3
knots. When the engine is revved up to 2650-1 , the speed
has increased to 15.7 knots.
2. Range, way made good per unit fuel and hourly consumption
are highly dependent on the engine revs. As an example, while
at 1000-1 revs the hourly fuel consumption is 7.6 liters.
At 2650-1 revs this has increased to 84.9 liters. Thus, the
hourly consumption has increased more than TEN fold. At the
same time, range and way made good per unit fuel has decreased
FIVE fold.
At this example the "good" revs are 1500 - 1750
revs. Specially the green curves show the "hump"
at these revs. Above these revs the range drops more significantly.
In
summary, whoever runs his/her engines calmly, reduces engine
wear, saves money and has the comfort of a larger range. Whoever
"beats" the engines harm the environment and themselves..
| Notes: |
|
| [1]Original
tables from PMY magazine
|
| rpm |
Sea
Mile/Gallon |
Speed(Knot) |
Gallon/Hour |
Sea
Mile / Gallon |
Range |
Noise(dB) |
| 1000 |
7.3 |
6.3 |
2.0 |
3.63 |
1308 |
73 |
| 1250 |
6.6 |
7.5 |
3.0 |
2.87 |
1032 |
73 |
| 1500 |
9.6 |
8.3 |
6.0 |
1.6 |
576 |
74 |
| 1750 |
10.6 |
9.2 |
8.0 |
1.3 |
477 |
75 |
| 2000 |
11.3 |
9.8 |
10.6 |
1.1 |
382 |
77 |
| 2250 |
12.3 |
10.7 |
14.0 |
0.9 |
316 |
78 |
| 2500 |
16.4 |
14.3 |
18.2 |
0.9 |
324 |
79 |
| 2650 |
18.1 |
15.7 |
22.4 |
0.8 |
290 |
80 |
| Boat |
Grand
Banks 36 MY |
Test
Conditions |
| Length
OA |
11.23
m |
Temperature |
21
ºC |
| Beam |
3.86
m |
Humidity |
%85 |
| Fuel
Capacity |
1515
l |
Wind |
No
wind |
| Draft |
1.22
m |
Sea
Condition |
Very
Calm |
| Displacement |
12.2
ton |
Fuel |
½
capacity |
| Engines |
Dual
210-hp Cummins 6B15.9M |
Water |
Full |
| Transmission |
Twin
Disc MG 5050 2.54:1 |
Crew |
3 |
| Propellers |
28”x25”
3-blade bronze |
Load |
Light |
The
speed has been measured as average of two direction by radar.
Source:
Powerboat & Motoryacht, January 1996, page 92 |
