Prop Chart for Model Airplane Engines

           




Starting propellor sizes are mid range pitch props that should fly just about any plane designed for that size engine.  Use these first as in most cases they will be close to the correct size.  Then use trial and error to fine tune maximum performance from your ship by trying the alternate props.  If none work better stick with the recommended starting prop.

Two Stroke Engines


 
Engine Size Starting Prop Alternate Props
.049

6x3

5-1/4x4, 5-1/2x4, 6x3-1/2, 6x4, 7x3
.09 7x4 7x3, 7x4-1/2, 7x5
.15 8x4 8x5, 8x6, 9x4
.19 - .25 9x4 8x5, 8x6, 9x5
.20 - .30 9x6 9x7, 9-1/2x6, 10x5
.35 - .36 10x6 9x7, 10x5, 11x4
.40 10x6 9x8, 11x5
.45 10x7 10x6, 11x5, 11x6, 12x4
.50 11x6 10x8, 11x7, 12x4, 12x5
.60-.61 11x7 11x7-1/2, 11x7-3/4, 11x8, 12x6
.70 12x6 11x8, 12x8, 13x6, 14x4
.78 - .80 13x6 12x8, 14x4, 14x5
.90 - .91 14x6 13x8, 15x6, 16x5
1.08 16x6 15x8, 18x5
1.20 16x8 16x10, 18x5, 18x6
1.50 18x6 18x8, 20x6
1.80 18x8 18x10, 20x6, 20x8, 22x6
2.00 20x8 18x10, 20x6, 20x10, 22x6


Four Stroke Engines


 
Engine Size Starting Prop Alternate Props
.20 - .21 9x6 9x5, 10x5
.40 11x6 10x6, 10x7, 11x4, 11x5, 11x7, 11x 7-1/2, 12x4, 12x5
.45 - .48 11x6 10x6, 10x7, 10x8, 11x7, 11x7-1/2, 12x4, 12x5, 12x6
.60 - .65 12x6 11x7-1/2, 11x7-3/4, 11x8, 12x8, 13x5, 13x6, 14x5, 14x6
.80 13x6 12x8, 13x8, 14x4, 14x6
.90 14x6 13x6, 14x8, 15x6, 16x6
1.20 16x6 14x8, 15x6, 15x8, 16x8, 17x6, 18x5, 18x6
1.60 18x6 15x6, 15x8, 16x8, 18x6, 18x8, 20x6
2.40 18x10 18x12, 20x8, 20x10
2.70 20x8 18x10, 18x12, 20x10
3.00 20x10 18x12, 20x10


 

Remember...
Install the prop with the curved side of the blade facing forward and tighten the prop nut or bolt with the proper size wrench.
Recheck the tightness of the nut or bolt often, especially on wood props which tend to compress and loosen more often.
When starting the engine, keep spectators at a safe distance clear of the model and out of the path of the propellor.
Keep hands away from the prop as much as possible.  Use an electric starter or if you're going to start by hand use a chicken stick.
Keep face and body out of prop arc as engine is started and run.
Never throw anything into the prop to stop the engine.  Pinch off the engine's fuel supply.
Make all adjustments from behind the prop except on pusher installations.
Discard any prop with nicks, scratches, splits, cracks or any other sign of damage.  Never attempt to repair, alter or bend a prop.
Don't run an engine in areas of loose gravel, sand or grass as the prop can throw such materials into your face and eyes.
Keep loose clothing, shirt sleeves and other such items away from the prop and avoid carrying items that can fall into the prop such as pens, screwdrivers, etc when starting the engine.
Be sure to keep the glow driver wire out of the prop path.
If a spinner is used, make sure the prop cutouts clear the propellor blades.