How do I know what prop to put on my boat?

Asked by: Blaque Bray

Selecting the correct prop should result in your engine running within the designed rpm range at Wide Open Throttle (WOT). Your owner’s manual should include this spec—usually 5000–5500rpm for an outboard or 4200-5000rpm for a sterndrive—or your mechanic or dealer may know.

How do I choose the right prop for my boat?

When choosing a propeller, choose a pitch that will keep the engine RPM in its recommended operating range. Going under the range will cause the boat to lug, while going over can cause engine strain. Blades have other important features built into their design. Rake is the angle between the blade and the hub.

How do you tell what size prop you need?

Propeller Sizes are given in a set of numbers, e.g. 13×17 or 19×23 usually labeled on the propeller. The first number is the Diameter (width of the circle of the blades) and the second is the Pitch (theoretical travel distance of the angled blades in one revolution). Two other design features include Rake and Cup.

How do I determine the pitch of my boat propeller?

It's stamped here in the hub. The first number will always be the diameter the second number will always be the pitch for your.

Which is better 3 blade or 4 blade prop?

3 or 4 Blades? A 3 blade propeller usually offers top speed performance while a 4 blade propeller provides maximum thrust and smooth cruising operation. Four blades have some features of their own, though. They often provide more lift at the stern which will help accelerate the hull, especially if it is stern heavy.

What pitch prop gives more speed?

The lower the prop pitch, the better your hole-shot. However, this comes at a price: top speed. The lower pitch makes the engine reach maximum rpm at slower speeds. Conversely, a higher pitch will deliver greater top speeds, but slower acceleration.

What does a higher pitch prop do?

Pitch measures the forward movement of the propeller’s blade during one complete revolution. This is measured in inches. Lowering prop pitch will increase acceleration and thrust. Increasing prop pitch will make the boat go faster (provided the engine has enough power to keep the RPMs in the optimum operating range.

What’s the difference between a 19 and 21-pitch prop?

A simple explanation of prop pitch indicates that a 21-pitch prop, if turning in a thick substance, will push your boat forward 21 inches for every revolution of the blades. Conversely, a 19-pitch propeller would move your boat forward 19 inches.

What does a 21-pitch prop do?

The Mercury manual defines pitch as “the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood.” For example, a 21-pitch prop would move forward 21″ in one revolution. The lower the pitch, the better the holeshot.

What prop makes a boat go faster?

If you are running an aluminum prop, changing to even a basic stainless steel prop will usually improve top speed. Because stainless steel is stronger than aluminum, the blades on a stainless prop can be thinner, which reduces drag in the water.

Will a 5 blade prop make my boat faster?

In recent years, 4- and 5-blade props have become popular because they suppress vibration and improve acceleration by putting more blade area in the water, especially when the prop is breaking the surface. They can also provide more bow lift for added speed.

What will a 4 blade prop do?

The increased blade area afforded by the addition of the fourth blade can provide increased water displacement capability, lift, and grip, as compared to a 3-blade propeller. In terms of actual boat performance, these characteristics can combine to enhance: Handling. Hole Shot.

Is a 2-blade prop faster than a 3 blade?

The answer is pretty simple. A 2-blade propeller is, indeed, faster than a 3-blade propeller. While a 3-blade propeller creates lift faster, it’s also heavier and slower in operation.

How much faster is a 3 blade prop than a 4 blade?

At the higher end of the RPM scale, the 3 blade propeller will almost always outperform the 4 blade propeller, so you can expect to lose about 5% of the top speed with a 4 blade propeller.

What is the difference between a 2-blade and 3 blade prop on a boat?

Three Blade



They have a major advantage when going against heavy winds and seas or a current as they will keep your boat speed by up to 30% better than the two blade. Moreover, they will run much smoother and reduce vibrations as it is balanced around 3 or 4 points as opposed to 2.

Why do some boats have 2 props?

When maneuvering at low speeds, dual props improve thrust and handling in reverse because the boat is never backing or steering away from the bite of the prop blades. This can make it easier to control the boat around the dock.

How many blades does an outboard motor have?

Three Blades or Four? In general, 3 blade props are the most common. They are available in wide size ranges and cost less than 4 blades. They typically yield a slightly higher top end speed than 4 blades.

What is the difference between a 3 and 5 blade prop?

It's a little less sensitive to trim. This high five is only thirty half inches in diameter and feels much smoother at lower pan than the big revolution.

How can I get more speed out of my boat?

The first is reduce weight weight kills speed. Now that means removing unnecessary gear from your boat. And it also means draining down tanks like your holding tanks. Your water tank perhaps.

Is 35 mph fast for a boat?

Even under full load conditions, you can go to 30 mph. From my experience, the optimum speed for water sports is 15 to 35 mph. So your pontoon might be a little slow but will be just fine for any water sports you like to do.

What RPM should my boat run at?

Most mechanics and engineers suggest the best cruising speeds are achieved at 3400 and 3800 rpm respectively.

How far below the boat should the prop be?

If you have a short shaft motor, the top most part of the transom and the lower most part of the boat should be about 15 to 16 inches. For a long shaft, I think 20 to 21 inches is correct.

How do I know if my outboard is mounted too high?

If it’s too high, the propeller tends to ventilate, losing its bite on the water and blowing out while turning and in steep seas. “If the prop consistently ventilates when heading down a steep wave, the outboard is probably set too high,” says Dean Corbisier, advertising and public relations manager for Suzuki Marine.

How do you tell if your boat needs a short or long shaft?

The way that we do that is we take out just a standard tape measure or a yardstick you measure from the transom all the way down to the keel transom to the keel.