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61fx or 75fx

Old 03-27-2011, 08:00 AM
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Default 61fx or 75fx

Hi. I just purchased a Seagull 71" Decathlon. I have an OS 61fx that is nib. The plane is in the 7 to 8 pound range. Calls for a 75 two stroke. Would the 61 be enough motor or should I go with a 75ax. Also what is the hp difference between the two. One more thing, I want to run a pitts style muffler. Is there any hp loss or torque loss between this muffler and the stock.
Thanks for any information on this subject
Old 03-28-2011, 07:05 AM
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Default RE: 61fx or 75fx

A .61 engine will easily fly a 7-8 pound airplane. In fact, it will fly airplanes up to about 12 pounds, depending upon the model type. The manufacturer may have recommended the .75-size engine because it will be a little better for aerobatic performance.

Power output:

.65 AX: 2.0 hp @ 16,000 RPM
.75 AX: 2.4 ps @ 15,000 RPM

ps is just about the same as hp. The 0.4 difference is when the engines are running at peak. You won't run the engines near that, so their power difference will be very much smaller.

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