Engine Or Propeller Balance Master

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For Rotax 912, 914Off-Set PropFor Rotax 582, 618For Rotax 377, 447, 503
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Balance Masters® are Patented, Designed, Manufactured and Distributed in the U.S.A. and are easy-to-install devices for propellers and Rotax engines. These devices cut the vibration factor on ultralight aircrafts by as much as 50 percent when both balancers are installed.

Balance Masters® are weighted with a high density liquid mass (Quick Silver). The physical principles of centrifugal and gyroscopic forces explain the action of the Balance Masters®. With the Balance Masters installed, the weighted liquid mass (Quick Silver) in the apparatus shifts during spinning, and adjusts to compensate for imbalances due to such factors as changes in flying conditions or warpage in the propeller, from nicks and rocks during takeoffs and landings. The Propeller Balance Masters® mounts on the propeller shaft or gear box in conjunction with the propeller. It is less than 7 inches in diameter.

The Engine Balance Master is made to fit most Rotax engines and bolts under the Starter Pulley on the Fly Wheel side of the engine. It is less than 5 inches in diameter. Each device weighs about 4 oz. Installation will take about 25-30 minutes using ordinary hand tools for each device.

Balance Master is designed to fit most propeller bolt patterns and Rotax engines from 277FA through 582. We will need to know the manufacturer of your propeller and engine model to determine the right configuration.

On engines with reduction gear box can be used a second balancer on the crankshaft, installed as shown in the diagram. The installation of the two balancers, the propeller and crankshaft, gives the highest level of vibration reduction.

15-05828: Off-Set Prop Balancer
15-09450: Balancer for engine Rotax 912, 914
15-05261: Balancer for engine Rotax 377, 447, 503
15-05260: Balancer for engine Rotax 582, 618


I bought this item because I know they work. What I didnt count on was shipping from the US to OZ inside a week!

Michael S Verified Purchase


March 3, 2022

I bought this item because I know they work. What I didnt count on was shipping from the US to OZ inside a week!

Michael S Verified Purchase


March 3, 2022

Fast delivery from Spruce. I got the 912/914 version, which fit the Rotax bolt pattern perfectly on my Saber prop spacer. Super easy to install, but I needed to get slightly longer prop bolts.

Steven E Verified Purchase


January 12, 2022

Everything looks Good!

Harlan P Verified Purchase


October 23, 2021

Works as advertised

Aaron S Verified Purchase


May 29, 2021

I use this balance on my Corvair powered KR2. The Corvair is already a smooth engine so this was added as insurance more than anything. Easy installation and seems to work good after 28 hrs. Really needs to be tested with a dyna-vibe. The manufacturer is pursuing an STC so maybe we will see some data from that effort.

December 13, 2019

I’m sure it works fine however it is not quite universal. There should be an alternative way to center the balance master on different prop spacer configurations. On mine, there is no centering nun so I can not place the round center hole of the balancer over the hub centering nub. I have yet to come up with a solution. Before purchasing - ask Aircraft spruce to post a picture of the prop hub that the balance master mounts to so you can compare.

Jeff H
May 26, 2020

Does not work, I have requested a full refund fromACS and so far crickets. Save your money.

Paul S Verified Purchase


September 28, 2021

It doesnt work on Autogyro configuration with Duc Helice props. Balancers inside diameter is 1/4 too small. Otherwise it would be great product to have.

October 12, 2020


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Can these be installed between the prop hub of a 582 and a ground adjustable GSC prop?

Yes, but you will want 15-05260.

Q: How much thickness does the balance master add on a 503 prop installation?

Per manufacturer: 0.038"

Q: Is the + off set prop balance master compatible with the Pipistrel Sinus (Rotax) 503 prop? And is it worth having both balance masters ( prop+503 engine)?

YES Prop is an offset and Engine is an HT503 is for air cooled. It is worth having both per the vendor.

Q: On a Rotax 912, does this device mount between the rear of the spinner back plate and the gearbox prop flange, or does it mount on the front of the spinner back plate between it and the prop hub?

This would mount between the rear of the spinner back plate and the gearbox prop flange.

Q: Would this work for a rotax 914 with a constant speed air Master propeller?

No, for the Rotax 912/914 you would want 15-10746.

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