All of your readings are far too cold, so you are taking them at the wrong location or under the wrong conditions.

- You must take the readings with the engine running full throttle.

- You must take the readings after the engine has run at full throttle for at least 1-2 minutes

- You must take the readings at the hottest part of the engine. Typically close to the exhaust or around the glow plug.


Note that you are only achieving somewhat normal RPM numbers with the 14x4MAS prop...

Roughtly speaking a 14x4 is about the equivalent of a 13x5 or a 12x6.... and amazingly (not) the latter is pretty close to the 12x7 I told you to try originally!

Do you understand the relationship between diameter and pitch when you move up and down sizes?

Roughtly speaking for each diameter size you go UP, you must reduce the pitch by one... ( this is not exact, so those who know better please don't point it out... )

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These are your own observed results ( I only used the same props as this is more meaningful ).

13x6mas S2 = 65 mph pitch speed, 1.86 HP, 10.69 lbs static thrust
14x4mas = 49 mph pitch speed, 2.46 HP, 18.66 lbs static thrust
14x6mas = 59 mph pitch speed, 1.85 HP, 11.76 lbs static thrust
14x8mas = 63 mph pitch speed, 1.32 HP, 7.67 lbs static thrust

So the 14x4mas is putting the "correct" load on the motor... adjusting to try to put the same load using a different diameter... puts you back to a 13x5, or a 12x6 prop!!!

Exactly what everyone has been telling you all along!



yachty: I feel your pain!!!