How to choose an upgrade prop for your brushless RTR RC boat

A well chosen prop for your RTR boat is the simplest and cheapest way to increase performance.

The most important thing is to not try and invent the wheel – get it wrong and your boat will either go slower or even possibly catch fire!

If it’s a popular RTR model you can be assured many people will have gone down the same path and the guess work can be taken out. Boat manufactures are are always going to be slightly conservative with prop selection, to give decent run time without causing excessive heat or strain on the electronics. As a general rule there is usually enough room to increase prop diameter by about 2mm over stock safely, as long as the pitch does not increase at the same time. Doing so will most likely increase top speed and acceleration without adversely affecting run time or causing damage to electronics. If by increasing the diameter (or pitch) you find your boat has not gained any speed then you have gone too far, the power output is not enough to turn the prop and you will most definitely encounter heat issues and lack of run time.

Obviously a simple prop upgrade will not turn a 50mph boat into a 90mph rocket ship. Companies like Traxxas and Proboat are not going to spend tens of thousands of dollars designing a new model then throw any old prop on there without testing all options. Put simply to dramatically improve the performance over stock you will need to increase the power output as well.

RCBB’s Traxxas Spartan prop upgrade will add around 5-6 mph, and the Traxxas M41 version produces a similar amount.

Proboat’s models like the popular Sonicwake, Blackjack 42 and UL19 use to great effect, with a slightly greater increase once setup properly.

One important point on RTR props is they are often made of plastic, which are not only easily damaged, but more importantly prone to distorting at high rpm. A CNC alloy or bronze prop will usually outperform its plastic equivalent for that reason alone.

Almost every RTR model no matter the brand will be supplied with a 2 blade prop. This is because a 2 blade prop will usually produce the highest top speed, whereas a 3 blade prop will accelerate quicker. As with any rule there will be exceptions, but its highly unlikely you will find a 3 blade prop with a higher top speed than a 2 blade in a single motor application. If you are wanting to experiment with 3 blades make sure to start with a smaller diameter, maybe in the region of 20% smaller than the 2 blade that the factory supplied.

If you want to experiment with larger pitches, the rule there will be to reduce the overall diameter. Increasing prop pitch can certainly increase speed, but every plus has a negative. High pitch will increase amp draw/heat and also reduce low speed acceleration, and going too far on the wrong hull may cause so much cavitation your boat may not even take off.

One other important factor is cooling. Most RTR boats run warm to hot out of the box. As soon as you introduce even the slightest amount more load you can run into overheating issues. If you are intending to run any prop other than standard you will most likely need to improve the cooling. Most RTR’s will have a single pickup rudder, feeding water through the esc, then to the motor. You can run an additional water pickup off the back of the boat or fit a dual outlet rudder and feed the esc and motor separately. sells these bolton upgrade cooling kits for almost every boat on the market, past and present.