One of the most critical aspects of every center console’s performance is at what RPM the vessel gets on plane. It is here that the Sharrow prop’s performance is remarkable. In a recent test conducted by Sharrow Marine on a Robalo R302, the company’s props show significantly more thrust in the critical RPM range of 2500 to 3500, than standard props.
In the chart above, it can be seen that the boat is nearly on plane at 2500 RPM and 15.4 mph. At 2700 RPM, the boat is firmly on plane (typically about 18-20 mph for these types of boats) with the Sharrow props. And, at 3000 RPM, the vessel was recorded going 25.4 mph. With the conventional stainless steel props, the boat was not able to climb over its bow wave at 3000 RPM.
Critical Point of Operation. Just as an airplane must reach a certain speed before it can take flight, so too, must a powerboat reach a certain speed before it can get on plane and level out. Further, just like an airplane, the thrust required for “take-off” depends on the weight of the craft. The greater the number of people on a boat, the more thrust is required to raise the boat up on plane.
Zeroing-in on the speed chart, we see that at 3000 RPM the Robalo R302 goes over 10.4 mph – or, 69% -- faster with the Sharrow props than with the conventional props. This occurs because of the greater thrust produced by the Sharrow props. Further, according to Sharrow, their props also raise the stern which helps keep the bow down.
The Importance of Planning Quickly
Who among us has not suffered the embarrassment in front of friends invited aboard, when the boat struggled to get on plane, and only did so with the engines loudly racing? Still worse, is the amount of bow rise which often obscures the horizon, restricting visibility, thus creating an unsafe few seconds of operation.
There are several important reasons why getting on plane quickly is important – and most revolve around safety. When a boat is struggling to get on plane, the operator has difficulty controlling the vessel as it can hunt from side to side, as it tries to climb its bow wave.
This is where novice operators can get into trouble by either slowly accelerating – which only prolongs the squirrely control – or, by slamming the hammer down with the result that the boat bursts forward leaving passengers with white knuckles, and possibly rushing up faster than anticipated on another boat or obstruction.
For more information about Sharrow Marine’s props, why they work, and BoatTEST’s reports on comparative tests it has conducted, click here.