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RC Boat Propellers: How To Choose The Right Size

RC boats offer a lot of thrills and a ton of fun, even for landlubbers. With their high speeds and amazing detail, it’s easy to see why these “seafaring toys” are increasingly popular with RC fans worldwide. In order to make them work properly, they’re going to need the right propellers.

How do you choose the right sized propellers for your RC boat? Picking the right “prop” for your RC boat involves knowing the diameter, the pitch, and the shaft size of your propeller. Once you know these measurements, you can choose an option safe for your boat.

A bigger propeller is not always the best option for your RC boat, and can even cause damage to your boat’s motor. To get the best possible size (and speed) for your RC sailing, it’s best to keep reading this guide. 

To get the best price for your RC boat propellers be sure and check here as well.

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How Do You Choose the Right Sized Propellers for Your RC Boat?

It’s important to remember that there is not “one perfect size” for an RC boat propeller. What size works for your RC boat will depend on a variety of factors, including the following:

  • Motor Strength
  • Pitch
  • Diameter
  • Shaft Size

Most top RC boating experts calculate the best size for their RC propellers by finding the total pitch of their potential “prop.” This calculates how far the boat should go after one full turn of the propeller. The higher the total pitch, the faster the boat will go. 

How Do You Calculate Total Pitch?

This is actually a little easier than it sounds. Total pitch is simply the measured pitch multiplied by the diameter of the boat’s propeller. 

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. It’s better to be safe than sorry in this matter.

Is Calculating Total Pitch A Reliable Measure Of Speed?

Total pitch is actually only accurate if there’s no “slip” of traction in the water, so it’s not really accurate in the real world. Depending on your boat type, you can expect anywhere from a 10 to 30 percent difference in the distance your boat travels.

How Does Propeller Diameter Factor Into Your Ideal Size?

The size of a propeller’s actual diameter will change the way your RC boat handles the water. Here’s what you need to know about diameter sizing:

  • The typical standard size for an RC boat propeller is between 65 to 80 mm for a gas-powered boat. If your RC boat is around the average size and weight, this diameter will work well for you.
  • Heavier boats need larger propellers. Larger, heavier boats will need more prop to push them through the water. It’s just physics! A larger propeller will give more force to push the boat. 
  • Remember to start small and test propellers out. If you aren’t sure how large a prop your RC boat can take, don’t worry. Test out your boat’s motors for 20 to 30 seconds with a potential propeller, then wait 5 seconds. Gently touch it. If it’s too hot to touch, you need a smaller propeller because the motor can’t handle it.

What About Shaft Size?

The propeller’s 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 boat’s propeller options, don’t be. Propeller diameters are made to fit shaft sizes, which are made to be big (or small) enough for their respective boats to handle. 

Understanding Your RC Boat Kit’s Propellers

Most RC boat kits come with more than one propeller, with many offering up at least three or four of varying sizes. This is by design, and each propeller is typically made for its own unique purpose. 

Some propellers, typically the smaller ones, are made for slow-speed cruising. The larger the propellers get, the more likely it is that they are meant for racing, specialty waters, and stunt steering. 

It’s important to remember that the inclusion of a propeller in your RC boat kit doesn’t mean that the prop is good to use for long periods of time at maximum power. Testing each propeller out can help you determine how conservative you need to be with your RC time. 

Learning About Boat Kit Propeller Compatibility

If you are relatively new to the world of RC boating, then all this talk about math, propeller testing, and engine burnout can be intimidating. After all, hobbies are supposed to be easy, right? Not a problem. There are some easy ways to handle finding new propellers for your boat:

  • Check out the name, make, and model of your RC boat kit. Boat kits made by major manufacturers are fairly popular and well-known in the RC world. In some cases, propeller makers will mention some of the more popular kits their props are compatible with.
  • Poke around online RC boating forums. The RC boating community is one that’s extremely supportive and open to helping newbies. Going onto online forums and asking for help as a newbie is a great way to get suggestions on propeller sizing for your boat.
  • It’s also totally okay to read reviews on propeller add-ons made for your RC boat kit. If your kit is extremely popular, you might find reviews that offer advice on propellers that are made with your kit in mind. Picking those propellers, or even just finding ones with similar measurements, is a good way to get great results.
  • Read your boat kit’s pamphlet. Some boat kits come with pamphlets that offer guidance on propeller sizing, as well as information about the best propeller material for your boat to use. Here’s hoping you didn’t throw out that pamphlet!

If you are a big DIY person you may consider making your own propeller at home. Here is a step by step of how to do exactly that!

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Final Notes About Sizing Your RC Boat Propeller

The world of RC boating is a diverse one, especially when it comes to boat types, sizes, and shapes. Choosing a propeller is rarely, if ever, a cut-and-dry matter. If you are still feeling lost about your propeller sizing, keep these tips in mind:

  • Always check your engine temperature after a dry prop run. In RC boating, a heated engine is a soon-to-be-dead engine. The cooler your engine runs, the better off your little boat will be. 
  • If you aren’t sure which propeller to choose for a race, test each out in waters similar to the type you’ll be racing in. This is the easiest way to ensure you’ll get the most accurate idea of how fast your boat can go. 
  • Get experimental with it. A lot of RC enthusiasts find their favorite boat props by sampling a wide range of them until one or two just do the trick. Though simple, this approach is surprisingly successful at pairing boats to great prop sizes.
  • Different conditions will yield different results. Water temperatures, wind readings, and even the overall weather reading of your boat’s speed and water handling. This means that a propeller that performed great one day might not be ideal the next. 
  • Never be afraid to ask for a little help. Every hobby has its own learning curve, and that includes RC vehicles. If you are feeling lost, ask someone for help. Even the boat kit’s manufacturers will be able to give you advice on where to start.