It has been described as a "magical" prop, with excellent performance over the whole rpm range, while it also achieves very low consumption, as it is characteristically indicated by its name.
This statement refers to the Enertia ECO, the design of which is of particular interest.
But is everything attributed to the Mercury propeller real?
The Enertia ECO prop was tested in comparison with the Revolution prop, one of the most famous propellers on the market. The results were clearly in favor of the ECO prop, which also demonstrated higher top speed compared to the Revolution prop.
However, I think that this comparison, in which the Revolution prop appears inferior to the ECO prop, is simply because these are two completely different propellers. Their differences are huge, while their orientation is completely different.
Does the very good performance of the ECO prop is due to its larger diameter and not due to the particular characteristics of its design? Would any propeller with a 16΄΄ diameter give better acceleration, higher speeds at low and medium rpm and, of course, lower fuel consumption compared to the Revolution prop?
Therefore, we cannot draw any conclusions about the performance of the ECO prop when we compare it to the Revolution prop. On the contrary, I feel that a comparative test of the ECO prop against a matching Suzuki propeller would be really interesting.
So, let's compare two propellers that share many characteristics:
- Same diameter
- Same number of blades
- Approximately same blade surface area
- Approximately same pitch
- Approximately same rake angle, which, however, highly increases towards the outer edge of the ECO prop blade, reaching 40 degrees.
We tested these propellers on a Suzuki 300hp engine which was mounted on the transom of Marvel 930. The tests were performed at the same time, in the same sea area, at the same direction and angles of trim and, of course, with the same load, in order for our measurements to be as objective as possible.
Observing the numbers in the above table we can easily see that the differences in the performance of the two propellers are minimal.
- Both propellers get the boat on plane at the same rpm with the exact same speed.
- They have the same speed at low and medium rpm, although Suzuki prop has slightly shorter pitch, while it appears to have lower fuel consumptions.
- ECO prop allows the engine to reach higher rpm despite its slightly longer pitch, which actually explains the final speed it achieves, which is higher by 0.5 knots.
- Suzuki prop ran faster up to 30 knots. We should note here that even the 20΄΄ pitch Suzuki prop we had tested gave us greater accelerations than the 19'' ECO one.
A very interesting peculiarity of ECO prop
As we can see in the picture above, one of the main design differences between the two propellers concerns their progressive rake. In the ECO prop, we observe a sharp cup on the outer edge of the blades, which has led its manufacturers to create a relative extension of the aft part of the hub. On the contrary, when it comes to the Suzuki prop, as in all propellers, the outer edge of the blade is cupping towards the opposite direction allowing the water to leave the prop.
In the ECO prop, owing to the above inclination of the outer blade which dramatically increases the rake, a greater volume of water is directed towards the propeller's hub. Theoretically, this means that the ECO prop ventilation is greatly limited in increased trim angles and when raising the engine higher. This allows us to raise our engine on the transom resulting in higher top speed and lower fuel consumption owing to the less exposure of the gearcase in the water. Virtually, the ECO prop appears capable of producing greater thrust in conditions where other propellers fail.
The following are the detailed measurements of both propellers
The Suzuki propeller
- gave us a much better throttle response due to its greater "bite" in the water
- gave us faster accelerations
- showed lower slip numbers over the whole rpm range, and thus gives us the same or higher speed despite its shorter pitch - except the final speed-
- kept the bow clearly higher, which was actually unexpectable because of the more sharp rake of the ECO prop, and it was as if the entire rib was running higher in the water, blowing really less spray.
- gave us the same and sometimes slightly higher speeds at low and medium rpm despite its slightly shorter pitch
- was more fuel efficient despite its shorter pitch
The ECO Enertia prop
- gave us an extra half a knot on the top speed, but this is due to its longer pitch
- gave us very smooth and soft riding at every engine's speed
- despite its longer pitch, it allowed the engine to reach higher rpm. This is due to its thinner blades, which allows us switch to a longer pitch propeller and therefore increase our top speed
- due to the special design of its rake, it is really worth trying higher mountings of our engine with what this entails.
About the Enertia ECO prop
According to the manufacturer, the blades of the ECO prop are thinner than the blades of the other stainless steel propellers because they are made of X7 SS Alloy, which is 30% stronger and four times more durable than stainless steel.
The ECO prop has a diameter of 16 inches and is available in a 17, 19, 21 and 23 pitch size.
The combination of the larger diameter with its higher degree of progressive rake results in a greater lift of our bow, lower overall boat drag and thus lower fuel consumption at cruising speeds, while it allows mounting our engine higher compared to the other Mercury propellers.
A great advantage is also that due to its thinner blades it allows our engine to increase its rpm, which enables us to try longer pitch propellers and thus get higher speeds.
I think that the ECO prop did not come to replace the Revolution or the Mirage Plus prop. It came to fill a large, that existed for so many years, concerning the matching of the propeller on large resistance hulls and larger or more heavily loaded boats which run with Verado engines. And now, with the new reinforced gears and slower propshafts of Verado outboards, it is time for the ECO props to give us great performance in specific conditions, where the other propellers can not perform.