Pitch Prop Vs 19 Pitch Prop: Which Do You Need
by Kyle WUpdated on April 23, 2021.
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Your boat is very much like your car without proper maintenance and the right parts, it will give you issues and might leave you stranded while out fishing for bass. The difference between your boat and your car is that the parts arent quite the same.
While it will do you well to know how to change a flat on your car, when it comes to boating, propeller diameter and pitch are some of the most important terminologies. This is because its your propeller that actually drives the boat. So understanding a bit about it could save you a whole lot of headache down the road.
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Whats The Difference Between A 19 And 21 Pitch Prop
Propeller pitch typically referred to as prop pitch, is essentially the distance a propeller would move in a single revolution through soft solid. So, in this case, a 21 pitch prop would move 21 inches forward in one revolution, and a 19 pitch prop would move 19 inches forward in one revolution.
Find A Replacement By Oem Part Number
If you know the OEM part number and basically just need to find the replacement, use the Prop Finder tool. Or search the pages and PDF guides below by your OEM part number to find a suitable replacement. Give us a call at 1-800-998-9508 or Intl. +1-206-780-5670 if you don’t find what you need and our boating experts will quickly help you locate a replacement.
- OEM Cross-Reference Table for Mariner, Mercury Outboard & Mercruiser Stern Drives
- OEM Cross-Reference Table for Mercury / Michigan Wheel / Quicksilver / Turbo / Turning Point
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Do All Boats Need A High Pitch Rc Propeller
Yes and no. Propellers with a higher pitch rating will travel further, but too much of a high pitch will eventually limit acceleration and speed. That being said, having a very low pitch prop on your boat can contribute to motor burnout. Its better to be safe than sorry in this matter.
Stainless Steel Vs Aluminum
Its a question of strength and performance. Aluminum propellers usually cost quite a bit less, however, stainless steel is over five times more durable than aluminum. If youre looking for quicker acceleration, superior top speed, or better overall performance, you should consider a stainless steel propeller.
Aluminum propellers arent expensive, they work well, and are relatively easy to repair, but aluminum isnt particularly durable, making aluminum props susceptible to wear and damage.
Stainless steel propellers cost more up front however, because stainless steel is stronger than aluminum, a stainless propellers blades are usually thinner and can be made in a wider variety of styles and shapes than an aluminum prop, thus the potential for better performance and increased service life.
Remember, it is stain-less steel, not stain-proof – a stainless propeller can still rust, so you need to keep it clean, just like the rest of your boat.
Three Blades vs Four Blades
Four blade propellers usually:
- Plane the boat faster than 3-blade propellers.
- Keep the boat on plane at a lower speed.
- Give improved mid-range speed at the same RPM as a 3-blade propeller.
- Provide quicker acceleration than most 3-blade propellers.
- Run smoother than 3-blade propellers.
- Have better holding power in rough conditions.
- Are less likely to ventilate in sharp turns.
- Provide better low speed handling.
- Are not quite as fast on the top end as a comparable 3-blade propeller.
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What Are Tooth Splines
A new propeller will only fit if the number of ´tooth splines´ on your propeller shaft is the same as the number of tooth splines on the inside of your propeller hub. When selecting your engine in our shop, it will automatically select the propellers with the right number of tooth splines. To verify if your new propeller will fit, you can check the number of tooth splines as mentioned on the product page.
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Boat Prop Selector Guide
Whether you are buying a new propeller for your boat, simply in need of a replacement for a prop you lost/damaged, trying to address a performance issue or you simply want to gain better fuel economy, we can help you find the perfect propeller for all of your boating needs. Propeller Depot offers the best pricing in the marine industry on all inboard, outboard, ski/wake and stern drive propellers. Order your boat propeller today from Propeller Depot and save.
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The Propellers Are Not The Right Size
Any practical boat owner knows to change the engine oil, swap out the impeller every year or two and change worn belts before they break, but the propeller is much more likely to be overlooked. Choosing the wrong-sized prop can affect boat performance, increase fuel consumption and potentially damage your engine and transmission.
Here are some ways you can tell if the propellers are too large or too small:
- Your boat is too slow to come on to the plane.
- The boat engine over-revs, although the boat is still moving slowly.
- If the prop is too big, the engine does not achieve maximum revs.
- The engine is using too much fuel.
Keep in mind that the wrong propellers will always harm your boats engine. Over time, you will have to repair or replace the engine, which means you will have to match the engine with the props .
Xoar Pjwwii 238 23 Rc Plane Propeller
EDITORS RATING: 4.7/5
Prop compatibility: Giant Scale RC aircraft w/ 50cc55cc gasoline engines: DA-50-R DLE-55, DLE-55RA, 3W-50i, ZDZ 56RV-J, DL-50, and XYZ 50
This high-quality prop from Xoar is the PJWWII. Its a 23 product made from top-grade German pollmeier black beech lumber. Its a purpose blade for giant-scale warbird gas-powered planes . The propeller boasts minimal breakpoint, elongation, and distortion properties. It comes pre-balanced both vertically and horizontally to reduce vibration to a minimum.
Cons: High cost, but then quality is paramount when flying giant-sized warbirds.
EDITORS RATING: 4.4
Prop compatibility: DJI Mavic 2 Pro/Mavic 2 Zoom camera quadcopter
These are quadcopter props for DJIs best-selling Mavic 2 Zoom and Mavic 2 Pro camera drones. The pack includes four pairs of black propellers with gold tips. These are quick-release ultra-lightweight blades with a foldable design. Theyre a perfect fit, easy to mount, well-balanced, and durable. They are also quiet, responsive, and smooth functioning.
Cons: Third-party props, so not quite to the same standard as OEM, but still quality for less money.
EDITORS RATING: 4.6/5
Prop compatibility: DJI Spark camera quadcopter
Cons: The props are a tad thinner and flimsier than the originals, but not by much.
EDITORS RATING: 4.4/5
Prop compatibility: Parrot Anafi camera 4K camera drone
Cons: These props are slightly louder than the OEM though not by much.
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When Choosing The Right Propeller For Your Boat Youll Also Want To Consider The Material Used Number Of Blades And Pitch
A lower pitch allows you to build up RPM quickly which is good for big boats with a heavy load.
But there will be less forward travel with each revolution so not good for top speed.
A higher pitch is slower to build up RPM resulting in lower pulling power and acceleration but a greater top speed once the vessel winds up.
Youll also need to know how to read the prop. Meaning how to identify the size, diameter and pitch of a propeller.
Most props have a series of numbers on the side or inside the hub.
A three blade prop, 18.75 inches in diameter with a 19 inch pitch will have the numbers 3 X 18.75 X 19.
Numbers are printed on the side of your prop tell you the number of blades, diameter and pitch of your prop.
If they are not printed on the side of the prop, look for the numbers inside the hub of the propeller to determine diameter and pitch.
What Problems Are You Looking To Solve
Is your boat sluggish coming out of the hole and slow to get on a plane? Are you not hitting the top speed you think you should? Do you want an improvement in fuel economy? Hoping for better all-around performance? Is your current prop blowing out or ventilating excessively in turns or when you accelerate? Are you looking to improve your boats watersports performance for tubing, skiing or wakeboarding? Once you have defined your goals, you can move on in the selection process.
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How To Balance Rc Plane Propellers
Balancing RC plane propellers is vital because it reduces or eliminates vibration. Too much vibration is potentially harmful to the model. Over time it can damage the engines bearings, motor, and even the airframe. The larger the model, the more critical prop balancing becomes. Theres a simple instrument called a prop balancer that every RC pilot should have in his or her toolkit.
These simple devices are invaluable, and they last a long time with proper care. The best way to highlight their features and how they work is with a few examples.
What About Shaft Size
The propellers shaft size is the size of the connecting shaft between the propeller and the boat. This is the only truly rigid aspect of choosing a propeller size your shaft size always has to remain the same.
If you were worried about the shaft size limiting your boats propeller options, dont be. Propeller diameters are made to fit shaft sizes, which are made to be big enough for their respective boats to handle.
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Brave New Blade Design
With modern propeller design and construction methods the three main criteria are no longer the only governing factors. Increasingly, shape is just as important.
If the diameter needs to be smaller to provide better acceleration then the blade area can be increased by adding more blades. For optimum performance, fuel economy, fast acceleration and smooth vibration-free running, it is the shape and cross section of the blades that make the crucial difference.
For the everyday boat owner blade shape is governed by the boats dimensions, its engine specifications and the owners choice of propeller manufacturer. High-tech computer-designed and machined propellers only become viable for yachts over 24m where the shape of the blades is tailored to the requirements of the vessel taking into account resistance as well as all the normal information required to build a propeller.
This Sunseeker propeller is a good example of what is required to propel a heavy high-performance craft. The total area is greatly increased by overlapping the leading and trailing edges of the blades. This avoids the problem of cavitation, but the blades are shaped to ensure water flows smoothly through the propeller
The shape of the older equipoise is reminiscent of the latest foil design although it has less blade area.
The round blade turbine propeller is still used on heavy displacement craft including commercial vessels. It has a large blade area and thick sections to resist damage.
How To Select The Right Propeller
There are a few important factors that go into choosing the right boat propeller. Because there are so many props to pick from, choosing the right prop on you own is risky. You must know your performance goals, engine information, and finally pitch to get it right.
A great option is to use the Mercury Prop Selector Tool. This tool works for most manufacturers including Mercury, Evinrude, Johnson, Volvo, Yamaha, Nissan, Honda, Suzuki, Tohatsu . It walks you through 4 steps in choosing the right prop the first time. If you choose not to use the tool, this article can still help you choose the right prop.
First choose your boat type: bass boat, pontoon, ski
Step 2- PerformanceNext, know your performance preferences.The most important consideration in finding a prop is to know your performance goals. Are you into high speeds? Expert handling? Fuel Economy? Accelleration? Or maybe you simply want overall good performance? This short video explains the differences so you get the right propeller the first time.
A secondary performance consideration is high altitude usage. Your boat will perform differently in high altitudes. If you boat above 3000 feet, you should take this into account.
STEP 3 Engine InformationNext, simply identify your current engine so that the prop will properly fit on the shaft. This quick video explains where to find your engine information. There should be a sticker on your transom bracket that identifies your engine year.
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How Are Your Wheels Turning
How can you determine if your boat needs a prop swap? The most effective method is to look at maximum throttle rpm and make sure its in the middle of the manufacturers recommended range.
If you have an outboard rated to turn 5500 to 6000 rpm, for example, and it turns 5400 or 6100 rpm, you have a problem. Lets say you have a 21 bay boat powered by a 200-hp outboard rated to turn within this range. With your usual load of gear, fuel, and passengers, at WOT it turns 5400 rpm. Top end is 40-mph. At a 4000-rpm cruise, you make about 35 mph. Your outboard is working harder than it should, and its lifetime may be reduced significantly.
A propellers pitch will affect speed, hole shot and RPM.
But dont blame the dealer or manufacturer. They, like most, probably put on a prop that spun up the proper rpm when the boat was field-tested before being sold. That was before you filled the tanks, put in your cast nets and safety gear, the anchor, and so on. Maybe you painted the bottom, too, or even added a T-top. Now, in real-world conditions, the original prop isnt proper.
Swap it out for a prop with an inch or two less pitch, and rpms will be in the recommended range. You should see an increase of speed at cruise of about one mph and about two mph at top-end. At the same time, your fuel efficiency is likely to improve.
The Meaning Of The Numbers On A Prop
Typically, most propellers will have specific information engraved on them. This information usually consists of two to four sets of numbers and letters.
One being the propeller diameter, the second being the pitch length, third representing the rotational direction and fourth being the bore/shaft diameter.
An example of these numbers displayed resembles the following: 15.6 x 15 | RH | 1 ¼
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How To Select The Proper Boat Propeller
Selecting the proper boat propeller is absolutely critical to the performance of your boat. But how do you select the correct prop for your boat? There are a lot of confusing details when choosing propellers…pitch, aluminum vs. stainless steel, repair vs. new, 3 blade vs. 4 blade. Before shopping for a propeller, either in person or online, it is important to answer a few key questions first.
- What kind of prop do you currently have?
- What outboard or outdrive or you using?
- Are you satisfied with top speed or hole shot of current prop?
Once you know where you are at, we can then help you decide what propeller is correct for you.
Is Your Engine Over Or Under Revving
Selecting the correct prop should result in your engine running within the designed rpm range at Wide Open Throttle . Your owners manual should include this specusually 50005500rpm for an outboard or 4200-5000rpm for a sterndriveor your mechanic or dealer may know. Allowing your engine to under rev or over rev at WOT can result in engine damage. Over revving or under revving can be corrected by selecting a prop with a different pitch.
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What Diameter Should You Choose
The size of the propeller is determined by two numbers: the diameter and the pitchthe number of the diameter is listed first. This is the diameter of an imaginary circle passing through the end of all the blades. It can be calculated by multiplying the distance from the center of the hub to the tip of any blade by two.
The larger the diameter, the more water the propeller will push, which will create more power. But a large diameter propeller also puts more strain on the engine. The choice of diameter depends on the space available under the anti-cavitation plate.
Choosing The Correct Propeller Will Give You The Best Of All Worlds For Performance Sailing Club Racing Motor Sailing Or Motoring
Should you ditch your fixed propeller? If your goal is to sail or motor to your destination more quickly, whether to the anchorage for cocktails or to your first waypoint on a passage, then a folding or feathering propeller delivers just that – less drag than all fixed propellers.
The average boat equipped with a folding or feathering propeller will gain between 0.75 to 1.5 knots of boat speed under sail over a boat with a fixed-blade propeller. In the folded or feathered position your boat will steer better and point higher due to unobstructed water flow to the rudder.
Many sailors often say We do not race, we do not need a folding or feathering propeller. But once they have seen equal sized boats passing them, they will consider this upgrade in order to sail and motor faster with the added benefit of 100% reverse thrust.
Investment Comparison
What is the extent of your winter budget, and what other investments for your boat are you considering? If you had the option to purchase a new genoa for the same price as a folding or feathering propeller, ask yourself the following questions:
- Will it increase your sailing speeds by approx. 1.0+ knots?
- Will it allow you to go to windward better in all conditions from flat calm to heavy winds?
- Will it maintain this performance over 10 or 15 years?
- Will it improve your backing down and manoeuvring?
- Will it increase your fuel economy and therefore increase your cruising range?
How do they work?
What to look for
Blade Shape
Diameter
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