A propeller to go faster and improve the mileage. It’s the Mercury Enertia Eco, compared here with the “old” Revolution 4. It’s mounted on twin 250 Verados to power the new Black Fin Elegance 9 rib.
We’re going to compare two propellers and there will be surprises. But first, we have to take a different approach to the issue. We normally measure liters (or gallons) per hour, a habit that comes from tradition and from commercial vessels, whose speed is pretty levelled. But it’s important to shift to kilometers per liter (or miles per gallon), which tells the actual distance covered with a unit of fuel: same as with cars, motorbikes, trucks. With smaller boats, let’s say under 60 feet, when the use of the boat is sporadic and the speed can vary much, it would be much more truthful to use these figures.
So, we are going to thouroughly test the the new Enertia Eco by Mercury Marine: a three-bladed prop whose efficiency is the most claimed advantage. We decided to compare it with a real benchmark, the four-bladed Revolution 4: one of the most appreciated models from Mercury and a reference point in terms of performance and economy.
The model we picked for our test is the new Black Fin Elegance 9 rib, one of the four models that carry the Elegance tag and will be marketed soon. Her siblings are the Elegance 7, Elegance 8 and Elegance, with the numbers clearly revealing the length in meters. The rib is powered by two Verados 250 (the top available choice), with Joystick Piloting system: but our focus is on the propellers, with some fun digressions in the high-speed territory.
Black Fin Elegance 9
It’s a classical open rib, organized with two large solariums, a large dinette and much space for storage and relax. The comfort is granted by the many standard features, such as the electric winch and the fresh water system, while piloting is made easier by the DTS remote control and the Vessel View 4 system to give full infos about the engines.
Abow the anchor locker is finished in teak and offers a good platform for diving, while the sun bed could be a bit larger when considering the length of the cockpit. As usual it hides much storage space underneath. The dashboard is essential: all the needed gauges, with the Vessel View 4 screens to give plenty of data, and a tilting bench in front. The windshield is correctly sized and protects the pilot without hindering aerodynamics. Abaft the driver’s seat (lift it and you find a refrigerator) the cockpit is completed by a U shaped couch and a removable table. The level of finishing is very high all around, to give the impression of a top quality product.
Enertia Eco Propeller
The Mercury Enertia Eco was designed to reduce fuel consumption by 10% at cruising speed, without touching performance and reliability. In order to achieve the goal, the blades are made in X7 Mercury stainless steel which allowed a progressive tilt angle. The active area is extra-sized and the diameter is 16”. The advantage is to better raise the bow of the boat, reduce the water drag, and consequently improve performance: in terms of mileage, lower planing speed, higher top. Enetria Eco is available with 19”, 21” or 23” pitch, clock- or counterclock-wise rotation, with a fixed diameter of 16” as mentioned.
While the sea out of Genoa seemed calm, the wind has increased and we have to stay close to the dock in order to have trustworthy measurements. First I go out with the new Enertia Ecos, 19” pitch. I collect all the data and wait for the numbers to speak. Back to the harbor, quick change of props and out again with the Revolution 4, till 19” pitch. The results of the tests are below, and the advantage of the new pair in terms of mileage is visible. In my opinion, it’s better to work on the trims already at medium speed, and not only to find the top pace like we are used to do. On a test run by Mercury in calm sea, the Enertia Eco have highlighted a remarkable advantage on the Revolution 4 especially in the speed range 25 to 30 knots ( 3000 to 3500 rpm).
Beside the fuel consumption, the speed figures clearly show the gain of the new blades. The few numbers that still confirm the validity of the Revolution 4 are planing time (2.9 secs vs 3.0), time from plane to top pace (12.9 secs vs 16.3) and minimum plane speed (11kn at 2100 rpm vs 12 at 2000).
As for the Black Fin Elegance 9, we are conquered by her maneuverability at cruising speed, while the sensitivity to beam waves is quite high at top pace. We recommend to install smaller engines, as we don’t consider reaching 50 knots as a priority for a rib whose comfort at cruising speed will be appreciated by many.
Tech specs Black Fin Elegance 9 Length 8,84 mt (29 ft) Beam 3,10 mt (10 ft 2 in) Tubular diameter 60 cm (1 ft 11 in) Dry displacement 1600 Kg Ma power 500 HP Passengers 14 Fuel 430 lt (113 US gal) CE certification B
Performance with Mercury Enertia Eco
1000 rpm 5,4 kn 6.2 mph 8,6 lph 0,63 nm/l 2.3 gph 2.74 mpg 65 db
1500 rpm 7,8 kn 9.0 mph 15,0 lph 0.52 nm/l 4.0 gph 2.27 mpg 67 db
2000 rpm 12 kn 13.8 mph 23,3 lph 0.52 nm/l 6.2 gph 2.25 mpg 77 db
2500 rpm 19 kn 21.9 mph 30,0 lph 0,63 nm/l 7.9 gph 2.76 mpg 78 db
3000 rpm 24 kn 27.6 mph 42,4 lph 0,57 nm/l 11.2 gph 2.47 mpg 79 db
3500 rpm 28 kn 32.2 mph 55,6 lph 0,50 nm/l 14.7 gph 2.20 mpg 80 db
4000 rpm 33 kn 38.0 mph 80,3 lph 0,41 nm/l 21.2 gph 1.79 mpg 81 db
4500 rpm 37 kn 42.6 mph 115 lph 0,32 nm/l 30.4 gph 1.40 mpg 83 db
5000 rpm 40 kn 46.0 mph 150 lph 0,27 nm/l 44.9 gph 1.03 mpg 85 db
5500 rpm 44 kn 50.6 mph 168 lph 0,26 nm/l 44.4 gph 1.14 mpg 87 db
6200 rpm 51 kn 58.7 mph 205 lph 0,25/nml 54.1 gph 1.08 mpg 88 db
Performance with Revolution 4
1000 rpm 5,2 kn 6.0 mph 8,3 lph 0,63 nm/l 2.2 gph 2.73 mpg
1500 rpm 7,2 kn 8.3 mph 13,8 lph 0.52 nm/l 3.6 gph 2.27 mpg
2000 rpm 10 kn 11.5 mph 21,1 lph 0,47 nm/l 5.6 gph 2.07 mpg
2500 rpm 16 kn 18.4 mph 29,2 lph 0,55 nm/l 7.7 gph 2.39 mpg
3000 rpm 22 kn 25.3 mph 39,7 lph 0,55 nm /l 10.5 gph 2.42 mpg
3500 rpm 27 kn 31.1 mph 55,8 lph 0.48 nm/l 14.7 gph 2.11 mpg
4000 rpm 31 kn 35.7 mph 72,8 lph 0.43 nm/l 19.2 gph 1.86 mpg
4500 rpm 35 kn 40.3 mph 102 lph 0.34 nm/l 26.9 gph 1.50 mpg
5000 rpm 39 kn 44.9 mph 140 lph 0.28 nm/l 37.0 gph 1.21 mpg
5500 rpm 43 kn 49.5 mph 192 lph 0.22 nm/l 50.7 gph 0.98 mpg
6200 rpm 49 kn 56.4 mph 203 lph 0.24 nm/l 53.6 gph 1.05 mpg
Slight sea, temperature 26° C (79 F), fuel 100 lt (26 US gal), no fresh water, passengers 3, clean hull
Package Black Fin Elegance 9 – Mercury Verado 200 HP€ 73.200 + VAT approx
Package Black Fin Elegance 9 – Mercury Verado 250 HP€ 75.600 + VAT approx