King Propulsion

Call Directions Website Contact the business

King Propulsion The right propeller for your sailboat, sized by a naval architect. US dealer for Bruntons propellers.

King Propulsion is a Naval Architecture Consultancy and marine parts supplier based in Virginia Beach, VA. King Propulsion is a distributor for Bruntons Propellers, supporting their Autoprop, Varifold and SigmaDrive range of products.

We've spent seven posts talking about propellers. Drag. Pitch. Reverse thrust. Cavitation. Fuel economy. Engine loading....
10/15/2026

We've spent seven posts talking about propellers. Drag. Pitch. Reverse thrust. Cavitation. Fuel economy. Engine loading. But eventually engineering has to leave the drawing board and go to sea.

And few places provide a tougher test than Antarctica. Xplore is a 67-foot Challenge business-class yacht displacing 41 tons and powered by a 130hp Perkins diesel. Skipper and expedition leader Stephen Wilkins takes her somewhere most of us would prefer not to discover a propulsion problem: The Southern Ocean and Antarctic pack ice.

With some 300,000 nautical miles of sailing experience behind him, Wilkins needed a propulsion system that could deliver power, reliability, simplicity, economy and low drag under sail. Xplore was fitted with a 23” Bruntons Autoprop Model H9 and then they went to work.

Over 13,500 nautical miles of motoring and motor-sailing, Xplore typically operated the engine between 900 and 1,200 rpm while motor-sailing and never above 1,600 rpm under straight power. But here's the part that caught my attention. In pack ice and heavy wind, the Autoprop's automatically adjusting blade angle allowed the propeller to respond to the load and deliver thrust where it was needed. And because the blades present their leading edge correctly in both directions, Wilkins reported equal thrust in forward and reverse. That's rather useful when the water around you contains ice.

Then there's the other side of the equation. Shut down the engine. Lock the shaft. And sail. Wilkins reported an increase of between three-quarters and nine-tenths of a knot under sail with the shaft locked. For Xplore, that's not just a number on a speed display. The yacht operates to demanding schedules with a target of 180 nautical miles per day. A little less drag, a little more efficiency and a little more speed become meaningful when they're multiplied across thousands of ocean miles.

Perhaps the most telling comment from Wilkins was also the simplest. After Xplore's first successful Antarctic season, he said the Bruntons Autoprop propulsion system had: “not missed a beat.” That's a rather different test from motoring out of the marina on Sunday morning. Most of us aren't taking our sailboats into Antarctic pack ice. But the engineering questions are exactly the same: Can I trust it? Will it give me the thrust I need? Will it work well in reverse? What happens when I'm motor-sailing? What happens when I shut down the engine and actually sail?
Those are the questions worth asking before choosing a propeller. If you're coming to thew Annapolis Sailboat Show, come see us at Booth YB3 near the Marriott hotel. Tell us where your boat is going - It probably isn't Antarctica. But we'll still take the propeller question just as seriously.

After six posts about fixed, folding, feathering and self-pitching propellers, here's the most important point of the se...
10/15/2026

After six posts about fixed, folding, feathering and self-pitching propellers, here's the most important point of the series: the propeller doesn't work by itself. It's part of a propulsion system, and choosing the right one takes more than deciding on two, three or four blades.

To size a propeller properly we need the engine's maximum horsepower and rpm, the gearbox reduction ratio, the shaft or saildrive, and the boat itself: waterline length, displacement and the space available behind the hull. From those we work out diameter, pitch, hub and blade configuration.

One principle is especially useful. For the best efficiency we normally want the largest diameter the aperture and clearance will allow. A larger, slower-turning propeller is generally more efficient than a smaller, faster one, particularly on a displacement sailboat or catamaran. But the engine and gearbox have to be able to turn it, so even that rule isn't applied in isolation.

Which is why I don't much like the question “What's the best sailboat propeller?” There isn't one.

The better question is: what's the best propeller for my boat, my engine and the way I sail?

Here's the good news for the show. You don't need to arrive with a folder of numbers. Tell me your engine make and model, and I'll look up its power and rpm and check the propellers already fitted to boats like yours in the Bruntons installation records. Then tell me what you'd like to improve: less drag under sail, better reverse, less prop walk, lower cruising rpm, better fuel economy, easier motor-sailing, less noise.

In a few minutes you'll have a sizing for each type that suits your boat, with show pricing, on a postcard to take home. Anything we can't check on the dock, such as the gearbox ratio or shaft size, we confirm afterwards before anything is ordered.

Come and see us at the Annapolis Sailboat Show, Booth YB3, City Dock, October 15–18. Tell me your engine model and I'll size your propeller while you're there. You'll walk away with your sizing and show pricing on a postcard. No numbers needed: just know your boat and how you use her.

You're motoring along comfortably. Then the rpm comes up and somewhere beneath the aft cabin... The boat starts talking ...
10/15/2026

You're motoring along comfortably. Then the rpm comes up and somewhere beneath the aft cabin... The boat starts talking to you.

Noise. Vibration. Maybe something that sounds decidedly unhappy.

It's tempting to blame the engine. But the problem may be happening several feet behind it at the propeller.
One of the less glamorous — but very important — subjects in propeller selection is blade loading. Folding and feathering propellers face a geometric limitation that fixed propellers don't - their blades must fold together or rotate past one another. That limits how much blade area the designer can use. And when a propeller has to transmit substantial horsepower through limited blade area, blade loading rises. Push that far enough and you can encounter cavitation, noise and vibration. This becomes particularly important as horsepower and displacement increase.

A propeller that works beautifully on a moderate-displacement cruising boat isn't automatically appropriate for a heavy yacht with a powerful engine. That's also why simply asking “Two blades, three blades or four?” doesn't tell us enough. We need to know what those blades are being asked to do. How much horsepower? At what shaft rpm? What displacement? What diameter can physically fit? What clearance is available? What sort of boat and how will it actually be operated?

Propeller engineering is a system problem.

Engine + gearbox + shaft or saildrive + propeller + hull.

Change one part and you can affect everything else. If your boat develops propeller noise or vibration under power — or you're contemplating changing propellers — bring the details to us at Bruntons Propeller Booth YB3 at the Annapolis show. Sometimes a conversation about an annoying vibration turns into a much more interesting discussion about what is actually happening underneath the boat.

Next: Before you buy a propeller, know these numbers.

Here's an interesting engineering problem. A conventional fixed-pitch propeller has to operate in all sorts of condition...
10/15/2026

Here's an interesting engineering problem. A conventional fixed-pitch propeller has to operate in all sorts of conditions — leaving the marina, cruising under power, pushing into a head sea and motor-sailing — with essentially the same pitch. But the load isn't the same in all those conditions. So, what if the propeller could adapt?

That's the idea behind the Bruntons Autoprop. Instead of locking the blades at one predetermined pitch, the Autoprop allows them to adjust their pitch automatically. Centrifugal and hydrodynamic forces acting on the blades find the appropriate angle for the power and rpm being delivered at that moment. The result is particularly interesting for cruisers.

At cruising speeds, the propeller can produce the required thrust at lower engine rpm, reducing fuel consumption. The article reports fuel savings of as much as 20 percent.
But one of my favorite examples is motor-sailing. Imagine you're motoring at a particular speed and then the breeze fills in. You unfurl the genoa. Now the sails are helping drive the boat.

With a conventional fixed-pitch propeller, maintaining that higher boat speed can require increasing engine rpm. The self-pitching propeller responds differently. As the sails contribute more driving force and boat speed increases, the blades increase their pitch.

The propeller adapts to the new condition. At low speed, the opposite characteristic becomes useful. The fine pitch used during maneuvering helps virtually eliminate prop walk, and the blade's leading edge presents correctly in both forward and reverse.

Then shut down the engine and sail, and the blades move into a low-drag position. That's why I find self-pitching propellers interesting as a Naval Architect. It's not simply about making a boat faster. It's about matching the propeller more closely to what the boat is actually doing.

If you're coming to Annapolis and spend a lot of time cruising or motor-sailing, stop by Bruntons Propeller Booth YB3. Tell us how you use your boat and how you use it. We can talk about whether a self-pitching propeller makes sense for your particular installation.

Next: That noise from the aft cabin may be trying to tell you something.

Come find the right propeller for your sailboat!
10/04/2026

Come find the right propeller for your sailboat!

Come see us on Booth YB3 with Bruntons Propellers to find out the right propeller for your sailboat!
10/01/2026

Come see us on Booth YB3 with Bruntons Propellers to find out the right propeller for your sailboat!

14 Days to go until the Annapolis Sailboat Show!
09/30/2026

14 Days to go until the Annapolis Sailboat Show!

There's an old temptation among boat owners: If a little is good, more must be better.Propeller pitch is one place where...
09/29/2026

There's an old temptation among boat owners: If a little is good, more must be better.
Propeller pitch is one place where that thinking can get expensive.

Feathering propellers have an interesting advantage: their pitch can be manually adjusted. That means you can change the pitch to better suit the boat. Sounds simple. But here's the catch.
Increasing pitch may improve performance at cruising rpm — but it also increases the load on the engine and reduces the maximum rpm the engine can achieve. And that's important.

Modern marine diesels are designed to reach their rated maximum rpm under load. If you've added so much pitch that the engine can no longer get there, you've effectively overloaded the engine. In other words, you may have “improved” your propeller while making the propulsion system worse.

Feathering props have some genuine advantages. Under sail, the blades rotate to present very little resistance to the water. They can work particularly well on long-keel boats where the propeller operates inside a relatively tight aperture. And because the blade's leading edge presents correctly in both directions, they can produce good thrust astern.

But there is a compromise. The flat blade geometry of a feathering propeller isn't as hydrodynamically efficient under power as the twisted blade of a conventional propeller. That's an important point because propeller selection is always a balancing act.

Sailing performance.
Motoring efficiency.
Reverse thrust.
Engine loading.
Noise.
Maneuverability.

There isn't one magic number — and there isn't one propeller that's automatically right for every boat. If you've adjusted the pitch on your propeller — or you're wondering whether your existing prop is properly matched to your engine — come see us at Bruntons Propeller — BOOTH YB3 at the Annapolis Sailboat Show. Bring your engine's rated horsepower and rpm, gearbox reduction ratio and current propeller size. Those numbers tell quite a story.

Next: What if the propeller could choose its own pitch?

Come see King Propulsion and Bruntons Propellers at the Annapolis sailboat Show at booth YB3! We will be located close t...
09/29/2026

Come see King Propulsion and Bruntons Propellers at the Annapolis sailboat Show at booth YB3! We will be located close to the Marriott hotel in the harbor. Don't forget your boat information to find out about the right propeller for your boat.

The folding propeller has a wonderfully simple sales pitch: When you're not using it, get it out of the way. Under sail,...
09/28/2026

The folding propeller has a wonderfully simple sales pitch: When you're not using it, get it out of the way. Under sail, the blades fold together and present very little resistance to the water. For a sailor trying to eliminate drag, that's extremely attractive. But eventually every beautiful day under sail ends with something less romantic:

A marina.
A fuel dock.
A crosswind.
In reverse.

That's where propeller design suddenly becomes very real. Early folding props developed a reputation for weak astern performance because the blades had to fight the water flow as they opened. Modern designs have improved considerably. Some use blade overlap so that shaft rotation, centrifugal force and water pressure help the blades open — particularly in reverse.

Three-blade folders can provide performance under power close to a fixed prop in many conditions, although some may still have less “bite” during low-speed maneuvering. Four blades can provide smoother, quieter operation, particularly as horsepower and displacement increase. But adding blades doesn't magically solve everything. As horsepower rises, blade loading becomes increasingly important. Get the design wrong and cavitation, noise and vibration can become part of the package. You may also hear the evidence from the aft cabin every time you motor.

So when somebody asks me: “Is a folding propeller good?” My answer must begin: “On what boat?” That's the difference between buying a propeller and specifying one.

Coming to Annapolis? Bring us your boat model, engine horsepower and current propeller information at Bruntons Propellers at booth YB3. We'll give you something much more useful than “folders are good” or “folders are bad.” We'll talk about whether one makes sense for your boat.

Next: Why adding more pitch can actually give you less performance.

Address

19441 Golf Vista Plz, Ste 360
Lansdowne, VA
20176

Opening Hours

Monday 9am - 5pm
Tuesday 9am - 5pm
Wednesday 9am - 5pm
Thursday 9am - 5pm
Friday 9am - 5pm

Telephone

+17577392050

Website

Alerts

Be the first to know and let us send you an email when King Propulsion posts news and promotions. Your email address will not be used for any other purpose, and you can unsubscribe at any time.

Contact The Business

Send a message to King Propulsion:

Shortcuts

Share