There is no doubt that both 3-blade ECO Enertia and the 4-blade Revolution are two of Mercury's most intelligently designed propellers which indeed claim the title of best seller ones.
They are two propellers with huge differences between them, with completely different design features and of course with different orientation.
So, as we can not compare a sport car with a jeep, there can be absolutely no comparison between them. This "comparative" test has no meaning, not even for the specific boat-engine combination, and it is useful only to see the exact correspondence of pitch when switching from one propeller to the other without losing engine’s rpm.
We tested these propellers on a 2.6L Verado 350hp engine which was mounted on the transom of Corsair 29. The tests took place in the same sea area with the same direction, at the same time and angles of trim and, of course, with the same load, in order our measurements to be as objective as possible.
Comparative results that are valid only for the specific set-up, with the specific loads (206 litters of fuel – 2 people on board):
Taking a care look at the above table we see that ECO Enertia:
- got the Rib on plane at the same rpm
- was achieving shorter time to plane
- was accelerating faster until 30 knots
- was almost 5 knots faster at 3500 rpm despite its shorter pitch, with lower fuel consumption and a huge difference in slip percentage
- was faster by 1.5 knots at 4000 rpm with lower fuel consumption and slippage
- its efficiency began to slow down slightly at 4500 rpm as well as from 5000 to 6000 rpm where it showed lower speeds more than a knot, which is expected caused by its increasing drag due to the triptych: diameter-velocity- water’s behaviour change
- was clearly more economical at 3500 and 4000 rpm
- showed lower slip numbers across the whole rpm range, causing the higher cruising speeds it achieves
- reached exactly at the same WOT rpm and as expected it achieved a lower top speed by 2 knots.
By comparing the behaviour of the two propellers, ECO Enertia:
- was raising the bow higher during the planning mode
- was keeping the bow slightly higher at midrange rpm improving speed, acceleration and economy
- showed slightly more impressive throttle response and faster acceleration
- showed that it could work at slightly higher trim angles without ventilation tendencies thus no loosing its grip in the water.
The above performance is worthwhile only in this particular set-up and if we alter the loads, weight distribution or engine’s mounting height in this same boat-engine combination then the performance will be completely different.
The choice of the right propeller for our own Rib will depend on many factors such as the use of our vessel, the loads we usually carry, the weight distribution, the engine horsepower in relation to its shaft rpm, the engine’s mounting height, the sea area we are operating on, the type and length of our hull...
The above factors unfortunately interact with each other and so it is not so easy to discern which propeller will perform better in each condition and satisfy at the same time all the above factors.
We should never forget that each propeller is designed to deliver very specific performance and so has specific applications in specific set-ups.
There is no ideal propeller and no propeller does it all.
Each propeller, among other things, mainly comes to improve the behaviour of our hull or even meet specific requirements of our hull or our use, while at the same time it should match our engine as well as its mounting height.
What we have to keep from this test is that when we want to go from a 4-blade Revolution to a 3-blade ECO Enertia propeller maintaining the same engine’s rpm, then we have to drop down one inch of pitch.
In other words: The 19" pitch Revolution achieves similar rpm at WOT as the 18" pitch ECO Enertia.