Sharrow Props Gives 27% More Fuel Economy at 37 MPH w/3X MERCURY 350s
When it comes to boats like the SeaVee 390, which are designed and built for hard-core meat and trophy anglers, three things stand out as most important:
- Speed
- Range
- Fishability
When it comes to fishability, the SeaVee has all those bases covered, without question.
SeaVee 390 with tuna tower. When it comes to performance, windage is always a factor and its drag increases as the boat’s speed increases.
But what about speed? The SeaVee 390 comes with a variety of powering options, from twin 450s to quad 450s. This offers each owner the ability to dial in speed by choosing the engine combination that will give them what they want. But speed isn’t all about horsepower. Speed is a function of displacement, horsepower, bottom shape, and prop geometry.
The subject of this test—conducted by Sharrow Marine—was a 390 powered by triple 350 Mercury Verados, generating a total of 1,050 horsepower at 6000 RPM. Given her fully loaded displacement of over 17,000 lb. (7,973 kg.), she needs every bit of that power to go 48 MPH.
In the chart above, we see that the WOT speed topped out at 47.7 MPH with the conventional 4-blade props with a 19” pitch and a 14-5/8” diameter. The Sharrow prop was exactly one MPH slower at top end, but no one drives at WOT for more than a few minutes, and engine makers don’t recommend it.
Looking at the mid-range RPMs, where most people do operate their boat, the Sharrow Propellers offer significant speed advantages for this SeaVee 390.
Getting on Plane Faster
To get on plane, the engines need powerful thrust, and that is what Sharrow props are designed to produce. Note that at 2500 RPM, the Sharrow props have gotten the SeaVee to 15.7 MPH, and by 3000 RPM, they are pushing the boat at 21.2 MPH, solidly on plane.
Less thrust is created with conventional props, and they need more RPM to get solidly on plane. In this case, at 3000 RPM with the conventional props, the boat is still struggling to get over its bow wave, with the bow high and visibility reduced.
The Importance of Range
In the chart above, we see that the rig with the Sharrow props were more fuel efficient from 6 mph to 39 MPH–a range that covers most of the operation of this boat. The improvement in fuel efficiency ranges from 11%, all the way up to 27% at 37 MPH, a speed that this boat is likely to be driven when conditions permit. The range increase at all data points is nearly identical to this chart.
When we convert MPG to range–with a 10% fuel reserve held back for safety–we discover that at 22 MPH, the Sharrow props increase the boat’s range by 25%. Even more remarkable is that at 37 MPH, the boat’s range is extended 91 miles over that of the conventional prop. Clearly, owners of SeaVee 390s, regardless of which engine package they have, should consider Sharrow props if they want better range and fuel economy.
Range is something that large center consoles such as the SeaVee 390 should have to round out the “must haves” for boats of this type.
A More Efficient Propeller
The chart below shows the secret to the Sharrow prop’s success: far greater efficiency than the conventional prop design. It’s important to point out that the standard props tested are typically the best for each boat, engine, and application. The difference is that all standard props are old technology.
Old Technology Rules...for a While.
Both boat builders and their customers tend to be conservative when it comes to change.
Remember, as soon as builders saw their competition putting on joysticks as standard, and sales shifting in that direction, most builders got on board—making joysticks standard even though they cost $25,000 and more.
Likewise with stabilizing gyros–which are very expensive and may require a generator, too. Once the consumers started asking for the product, builders began rearranging their stringers to be able to take them if wanted. We think the day is rapidly approaching when builders will start making the Sharrow Propeller optional if not standard, equipment.