What distinguishes this propeller test from the two test reports published in BOOTE in 1998 and 2008? Answer: For the first time, an outboard motor is the "driving force". Another new feature is that only stainless steel propellers are being tested by the BOOTE testers.
The reason: the engine manufacturer's experience has shown that aluminium propellers are simply unable to cope with the power and high torque of the 300 hp Verado. Mercury's propeller recommendation for the six-cylinder engine equipped with supercharger technology is clear: "only stainless steel". You can live with that, especially as stainless steel propellers are an integral part of the "creed of the speedboat community" anyway.
The fact is that the blades of a stainless steel propeller are much thinner and yet stronger than those of its aluminium competitors and are therefore easier to shape and polish. In addition, a thinner blade requires less force to move through the water than a thicker one. All of this improves efficiency.
The only thing missing from Mercury at this point is an explanation as to why the five-bladed High Five, which the manufacturer attests excellent handling in rough water and impressive acceleration values, is not in the starting line-up for the test. The argument that it does not fit in with the boat-motor concept is difficult for us to understand. Following the cancellation of the aftermarket, the starting blocks in this test are all Mercury Marine propellers.
The first to take the plunge into the deep end isEnertiaThe new "WingFly" is a three-winged glider made from a special alloy whose wings are 30 % stronger and four times more stable than those of the test competition. It is designed to accelerate fuselages to high speeds quickly, especially when they are heavily banked.
The number 2 seed on the alphabetically ordered starter listLaser II is compact and lightweight and, according to the manufacturer, feels most comfortable on boats with a lot of power. The starting number 3 carriesMirage Plusan old acquaintance that is primarily intended to make cruisers, sports and racing boats fast. The fourth in the group, theTempest Pluswas developed for large, heavy boats with six-cylinder outboard engines and represents Mercury's entry into the "premier league".
This is where theRevolution 4. Mercury characterises the only four-wing model in the test as a smooth-running yet powerful sprinter with excellent holding power. The test series is completed by theVengeance. The sturdy all-rounder is the ideal "step up" from the aluminium to the stainless steel class.
The test boat shows that you can also establish yourself in the Premier League as a "light metal" boat. The aluminium hull of the Silver Condor 730, which is built with a 21° upturn, not only impressed the BOOTE test crew with its excellent handling characteristics. Never before has a propeller test been as comfortable and safe as it is today. This is undoubtedly also due to Mercury's F300 Verado.
The powerful six-cylinder engine moves the 7.27 m long boat, which weighs just under 2 tonnes with the engine and 200 litres of fuel on board, with a lightness that inspires. Digital gear shifting, electro-hydraulic power steering, a perfectly functioning power trim and the smooth running of the 2.6-litre engine deserve the title "finest". In other words, the best conditions for all test candidates.
It is important that the boat, motor and propeller are optimally matched to each other. This is not always possible with an "off-the-shelf" propeller - which is the only affordable option. This is why the search for the right propeller is often a search for the best possible compromise. In any case, the determined full load speed of the engine must be within the range recommended by the manufacturer. For the F300 Verado, this means speeds between 5800 rpm and 6400 rpm.
After a few test runs, propeller manufacturers and testers decide in favour of props with a pitch of 19 inches (the distance the propeller - moving in a solid material - travels in one revolution). The diameters (diameter of the circle drawn by the blade tips during one revolution) vary between 14 and 15 5/8 inches. The four-winged propeller has the same diameter as the largest three-winged propeller, but only a pitch of 17 inches.
A common feature of all test propellers is the so-called cup. The term "cup" refers to a small, outward-facing bulge on the trailing edge of the propeller blade. The cup improves efficiency and has the effect of increasing the pitch. The cup is also intended to prevent or at least reduce cavitation (vapour bubbles imploding on the propeller) and ventilation (the propeller draws in air from the water surface).
This is contradicted by the VPS (Performance Vent System) developed by Mercury, which all test propellers have with the exception of the Venge-ance. Behind the abbreviation "VPS" are holes in the propeller hub that can be completely or partially closed with plugs of different sizes. More or less open, the VPS directs outflowing exhaust gases onto the propeller blades in a controlled manner.
The aim is to artificially generate more slip, bring propellers with a large pitch up to speed more quickly and thus accelerate the boat better. To avoid any misunderstandings: slip is not a measure of the efficiency of the propeller, but the difference between the theoretical and actual forward movement of the propeller caused by the angle of attack of the propeller blades.
Important to know: Without an angle of attack, there is no slip, but also no pressure differences and therefore no propulsion. Unfortunately, the controlled air supply does not always have the desired effect. Our test boat reacted to the desired ventilation with vibration in the lower speed range and poorer acceleration values. For this reason, the VPS remained closed during the test runs.
A prerequisite for a true comparison is that all candidates are tested under the same conditions. For this reason alone, we looked for a test area - and found one on Lake Schwerin - that would not be affected by currents or waves.
Speed and acceleration are always measured at exactly the same point to ensure the same reception quality for the GPS and to rule out different echoes on the radar gun. It goes without saying that the fuel level is the same for all measurement runs.
There is also no discussion about the fact that the trim position of the engine must be adapted to the characteristics of the propeller in order to assess the handling behaviour in fast gliding, when accelerating and to reach the maximum speed. As usual, fuel consumption is also measured in addition to speed and acceleration.
Tempest Plus and Vengeance are the fastest when properly trimmed. They are the only ones to break the 85 km/h mark (exactly 85.2 km/h). Enertia and Laser II came in joint second with 84.6 km/h, leaving Revolution 4 (83.8 km/h) and Mirage Plus (83.7 km/h) at the back of the pack.
As expected, the Revolution 4 is the king of the sprinters, accelerating the Silver Condor 730 from 0 to 50 km/h in exactly 6 seconds. It also sets the best mark by a wide margin on the "long haul", the acceleration from 0 to 70 km/h. Exactly 10 seconds is the measure of all things here.
Tempest Plus, Mirage Plus and Laser II finished second, third and fourth in both disciplines. Enertia, only sixth in the 50-km race, was able to pass the "red lantern" on the long sprint course to Venge-ance, which had to let the test competition pull away by a clear 14.1 seconds.
Even if the fast guys are only marginally interested, all propellers run most economically at 50 km/h. Mirage Plus and Tempest Plus consume the best 0.74 l of premium petrol per kilometre. The consumption values of Revolution 4 and Enertia are just above this at 0.76 l/km. With the Laser II, the F300 Verado consumes a few more litres (0.78 l/km).
The powerful six-cylinder engine with the Vengeance develops the greatest thirst (0.81 l/km). In the full load range, the Vengeance can at least improve its fuel consumption by one place. Revolution 4, which had just come second, now slips down the rankings. Mirage Plus takes exactly the opposite route and climbs from fifth place to the top step of the winner's podium.
When it comes to assessing the handling characteristics, no measuring electronics are helpful, only the tester's "popometer". Of course, a propeller can only ever be as good as the fuselage it has to push. But in this case, as mentioned at the beginning, it is really excellent. It runs stubbornly straight ahead in displacement mode with all test propellers. Yaw: Not a thing.
The transition phase to gliding starts with the three-wing aircraft at 15 km/h with slightly more than 2000 rpm and is quickly overcome without the nose rising significantly. Only the four-wing glider manages this exercise a little faster at lower speeds. Position ¼ on the display proves to be the ideal trim for cruising at 50 km/h.
Trimmed in this way, the Silver Condor can also be steered into the tightest bends and circles at a speed of 65 km/h without propeller ventilation. It does not tend to hook or rock in any situation. On the contrary, it follows every steering movement super-softly and yet without delay. This remains the case even at higher speeds.
The three-wing aircraft only reach their limits when the engine is raised above the ½ mark on the trim indicator. Turns are still possible without any problems, only the tight roundabout is affected by ventilation. This means that the boat loses significant speed and can only be accelerated again when counter-steering.
As expected, the Revolution 4 has the best grip in these situations. While the Vengeance is the quickest to gasp for air, the Tempest Plus comes closest to the characteristics of the four-wing. When flying straight ahead, all test propellers can be raised to the maximum trim position without any noticeable ventilation. The maximum speeds that have only now been reached are also an indication of the lack of ventilation. It remains to praise the smooth running of the four-wing aircraft in all speed ranges.
Conclusion: If high top speed is at the top of the wish list, the Tempest Plus and the inexpensive "up-and-comer" Vengeance, which however disappoints in the sprint and consumption disciplines, are the first choice in this test. Those who prioritise comfort and excellent acceleration values will opt for the four-bladed Revolution 4, but will have to dig deep into their wallets.
The Mirage Plus and Tempest Plus are good all-rounders. The Laser II, on the other hand, is only in the top third in terms of speed. The same applies to the Enertia, which outperforms the Laser II in terms of consumption values, but shows weaknesses in terms of sprinting and price.
