Originally posted by Ed_Moorman
One of the replies mentioned using a "heavy" .91 4-stroke. The Saito .91, an AAC engine, weighs, according to their specs, 18.3 ounces with muffler. The OS .61FX is 19.4 ounces. I would imagine this is without muffler, but it is still an ounce heavier than the "heavy" Saito. Other 4-stroke .91s are much heavier, especially the Thunder Tiger at over 26 ounces.
Ed, according to the Tower web site the OS 61fx weighs 23.6 oz. with muffler and the OS 91fs weighs 23 oz. with muffler.
So it's not a question weight about as it is about fitting in the cowl and type of power and sound you want. Just bought a GP Shoestring and am pondering which engine to go with.
I really like the sound of a four stroke in a scale-like plane but the OS 61fx will fit entirely inside the cowl with a pitts type muffler. For me it's a tough choice to make as I like both engines.