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Test Mercury: every boat to her prop

It’s wrong to think that the sole engine is responsible for the performance of a boat. The propeller has the same importance, and this test run by Mercury shows it very clearly.

Mercury has always shown attention to the propeller choice. Their catalogue is by far the richest with solutions, models and measures, but lately they increased their attention to coupling engine and prop in the most efficient way, according to every boater’s needs. What can work in a situation can be the wrong solution in a different one, so there’s a lot to consider.

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Many tests for a better understanding

Several tests are needed in order to fully understand the performance of every prop, normally with the same engine and – when possible – on the same boat.

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In our case, the engine is a Mercury F150 EFI. Here’s a brief description. The F150 EFI is the first model developed with the ambition to be a benchmark in terms of performance and reliability. The block is oversized (3000 cc or 183 ci) but rather simple: four cylinders and two valves per cylinder. This unit could easily develop 250 HP but tuning it down to 150 HP means high torque and longer durability. The weight is one of the lowest in the segment (206 Kg) such as is the size. The easy-to-dismount cowling makes maintenance easier, along with no-spills oil change, accessible fuel filter and maintenance-free distribution system.

What do you mean by “range”?

Fuel consumption is one of the crosses to bear for a boater. But we need to be clear about the concept of “range”. The automotive world talks of kilometers per liter or miles per gallon, which is very clear to understand, so why the nautical one uses liters per hour? In these terms, probably a Ferrari revving at 5000 rpm uses much more fuel than a Fiat 500, but it’s also cruising at over 200 km/h and not – say – 100, so the distance covered is double. Shouldn’t it be the same at least for planing boats?

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All the answers are down here. The peculiar point of each test is always the same: looking at the consumption-at-revs graph it seems that there’s no difference among propellers. But if we take into consideration the range-at-speed, the differences become relevant. Here’s the results of the comparative tests.

Mercury F150 EFI 2×150 HP on Nuova Jolly 800 Pro

If you want to know more about Nuova Jolly 800 Pro rib, here’s our test with this very same engine. Mercury installed a couple of 19” Vengeance propellers, then a couple of 17” Revolution 4 ones. The formers are part of the Sport range and feature 3 blades in stainless steel, the latters are in the Comp range and are built in SS but with four blades. Test conditions saw a rib displacing 1760 Kg plus 150 liters of fuel and 50 of fresh water (around 50 US gallons in total), four passengers and calm water.

In blue you see the results with Vengeance, in green with Revolution 4.

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We can realize the following:

There’s a difference 7% to 20% to Vengeance’s advantage with higher pitch, between the cruise and top speed;

Such a difference strongly hinders the reliability of a fuel consumption test, if not properly analyzed;

The speed is higher with Vengeance;

Acceleration to 20 and to 30 knots is better for Revolution 4:

Vengeance        Revolution 4
0 – 20 knots             6”                5”
0 – 30 knots            8”                7”
0 – 40 knots            12”              13”

Which propeller is better? Much likely it’s the Vengeance 19”, but it also depends on the load as this is a professional rib so the displacement can vary a lot. In harder conditions, the faster acceleration of the 17” Revolution 4 may suggest it’s more indicated for such use.

Mercury F150 EFI 150 HP on Stingher Predator 650 TS

The single engine on this 6.50 meters rib has been tested with four different props. Beside the previous 19” Vengeance and 17” Revolution 4, there’s the 19” and 18” Enertia ones, both built in X7 alloy with three blades. The rib displaced 810 Kg plus 200 liters (50 gals) of fuel and water, 4 passengers aboard, calm water. In green Enertia 18”, in blue Enertia 19”, in red Vengeance, e in purple Revolution 4.

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According to the consumption-at-speed graph the Revolution 4 seems the best prop. But looking more carefully, the range-at-speed reveals exactly the opposite: the 17” Revolution 4 reveals to be the worst in terms of range.

In particular:
The best performing propeller is the 19” Vengeance, with an advantage up to 13% on Revolution 4 and around 5-10% on both the Enertia;

Range can vary a lot depending on the prop;

At different speeds, Enertia 18” has been better in a range and the opposite in another range;

Enertia both granted the highest top speed, slightly better than Vengeance;

Revolution 4 17” has given the slowest top speed, but it should be considered in case of high load.

This is the perfect opportunity to see how there’s not THE perfect solution to every situation. It all depends on the needs and use. A second set of propellers based on different utilization of the boat is a reasonable choice. Finally, we see how this rib – thanks to the favourable power-to-weight ratio – has granted the best fuel consumption (1.30 nautical miles per liter).

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Mercury F150 EFI 150 HP on Marlin 20 and Tullio Abbate Sea Star 21

As a mere benchmark, we publish also the results of the tet run on a Marlin 20 rib (6.60 meters and 750 Kg), and on a Tullio Abbate Sea Star 21 (6.20 meters and 600 Kg). Both these units have a higher real displacement when compared to the Stingher above, and both have been tested with just one prop: 18” Enertia for the Marin and 19” Enertia for the Sea Star. Higher weight explains lower range and top speed on the Marlin, while Tullio Abbate despite being heavier marks a good top speed and an excellent range, similar to Stingher 650.

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