With the new MerCruiser 4.5L V6 250 HP, Mercury expands to the inboard range the philosophy based on tough, simple and oversized engines, made to be reliable, low-maintenance and powerful
The main target was simple as much as surprising: move away from the ever more complex automotive blocks, and make a pretty simple engine, reliable and sturdy, good for developing an entire range and win over competitors for weight, size and performance.
So here’s the new MerCruiser 4.5L V6 250 HP, sterndrive inboard engine entirely designed in Fond du Lac, Wisconsin, where the Mercury Marine headquarters are located. And this already is a big news: until today, engines derived from blocks made for the automotive industry, while now the project is 100% “Made in Mercury”.
“We’re glad to start next-gen engines with this innovative unit – said Mercury Marine chairman John Pfeifer -. The MerCruiser 4.5L V6 sets new standards in acceleration and performance thanks to a great power-to-weight ratio: it’s 59 Kgs lighter than the ‘small block’ V8, with similar performance”.
The Test
In order to test in advance the new MerCruiser 4.5L V6 250 HP, and proof Mr. Pfeifer statements, we flown all the way to Fond du Lac for a sea trial on Winnebago lake. For us, a Sea Ray 220 Sundeck with single engine and a Sea Ray 310 Sundancer with twin units and joystick controls. The single mount could be compared to the glorious V8 5.0 ‘small block’.
The water of the lake is struck by strong wind, and waves force us to test the smaller boat on the river while the larger can face the “rough” water. No problem as there’s no need for a direct comparion between the single and twin solution. Once aboard the Sea Ray 220 Sundeck, 22 feet and less than two tons, I immediately appreciate how the small engine leaves much room in the engine bay. This is not an invitation to fill this space with any sort of gear…just a confirmation that the new unit is much more compact than the previous one, which we see in the boat beside us. And I have to add another point to the score board: this engine is pretty silent as well, 73 dB with open hood (and some wind in the background).
We move along the river, where in some parts we can speed up using all the thrust from the Bravo Three 22.5” propeller. Acceleration is very good, and our 200 Sundeck gets to planing in 5,7 seconds and revs up to 4900 rpm in 21,8 seconds. We can’t pass the 5000 rpm limit, while Mercury got to 5200 in their tests. But we have to take into account the stream of the river and the four people aboard. At minimum planing speed, we are revving some shy of 3000 rpm and burning less than 20 liters per hour. Cruising speed is around 30 knots. We can’t compare the new engine with the old V8 due to weather conditions, but we check the Company data and see a top speed of 42.7 knots at 5000 rpm using 74.5 lph, while at 4000 revs the fuel needed is 45.7 lph and the pace around 32 knots. The old small block V8 loses in terms of consumption, but can still raise the voice when talking of performance.
The 31 feeter Sundancer 3100 can challenge the wind and the waves of the Winnebago lake, and we get the confirmation of a great and seaworthy hull, perfectly at ease with the sharp and short waves of this water. I focus on the twin 4.5L V6: they mount again Bravo Three 22.5” props, but I can’t reach the 5500 rpm stated by the Yard and stop at 4800. Fuel consumption and top speed are very similar though, thus underlining how each test gets its own output. Despite the angry lake, I reach the planing in 6.5 seconds, another 20 and I get to 36 knots, not the stated maximum but close. What I really enjoy is how quick the engines pick up revs, because it definitely helps to maneuver the boat in these critical conditions. The feeling is a mix between safety and power. We can slow down to 2500 rpm still planing, so the engines sip gas frugally (and they’re not thirsty at cruising speed as well). On the way back we can also test the joystick controls, even too handy despite the wind and the stream.
The engine
V6, 4500 cc (274 cu. in.), 2 valve, with excellent figures in terms of weight and size. This is the ID of the new MerCruiser 4.5L V6. Some design choices have been aimed to reduce NVH (noise, vibration and harshness), for a better cruise. It’s also the first 6-banger compatible with SmartCraft system, which allows electronic inverter and throttle (DTS) for a smoother drive. Joystick control is another grat feature, as we could realize maneuvering amid waves and streams. More, the Adaptive Speed Control (ASC) automatically keeps the rpm steady, regardless of the load or the condition, wo the feeling when accelerating is of a better response, as there’s no need to continously adjust the throttle.
Cast-iron parts received a careful anti corrosion treatment, while many parts are made in aluminum or composites. Finally, maintenance has been taken into good consideration, with longer service intervals and access to all liquids on top of the engine. The new MerCruiser 4.5L V6 250 HP will make its European debut at the 2014 Genoa Boat Show, and it will be on the market right after.
Technical features
Model …………………… 4.5L V6
Power …………………… 250 HP (186 Kw) at 4800/5200 rpm
Cylinders …………………… V6, 2 valves per cylinder
Displacement ………………… 4.500 cc (274.6 cubic inches)
Bore and stroke ……… 101,6 x 92,0 mm
Injection ………… Multi Point electronic injection (MPI)
Lubrication………… 4,7 liters (1.24 US gal)
ECU control……… SmartCraft PCM 112
Prestazioni Sea Ray 220 Sundeck
rpm knots mph l/h gph db
1000 ……………… 3,3 3.8……………… 5,3 1.4……………72
1500 ……………… 5,1 5.9 ……………… 11,3 3.0……………. 72
2000 ……………… 6,5 7.5 ……………… 16,6 4.4…………… 76
2500 ……………… 9,7 11.1……………… 22,7 6.0…………… 78
3000 ……………… 17,8 20.5 ………….… 27,2 7.2…………… 79
3500 ……………… 24,5 28.2…………… 34,0 9.0 …………… 85
4000 ……………… 30,4 35.0 …………… 45,7 12.1…………… 85
4500 ……………… 34,9 40.1…………… 58,2 15.4 ……………86
4900 ……………… 39,1 45.0 …………… 71,8 19.0…………… 89
Test conditions
Calm river, clean hull, 4 passengers, fuel 120 lt (31.7 US gal)
PerformanceSea Ray 3100 Sundancer
prm knots mph lph gph db
1000 ……………… 5,2 6.0 11,1 ……2.9……… 64
1500 ……………… 6,7 7.7 … 14,1 ……3.7……..…67
2000 ……………… 8,2 9,4……25,1 ……6.6….……71
2500 ……………… 9,9 11.4 … 48,4 ……12.8………76
3000 ……………… 19,3 22.2… 57,1 ….. 15.1..…… 78
3500 ……………… 24,6 28.3… 64,3 ……17.0….… 79
4000 ……………… 30,7 35.3… 98,3 ……26.0………84
4500 ……………… 36,2 41.7… 121,0 … 32.0……… 85
4800 ……………… 38,9 44.8 …151,2 … 39.9……… 87
Test conditions: Moderate lake, clean hull, 4 passengers, fuel 250 lt (66 US gal)
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