Mr67Stang

I run OS engines almost all the time. A buddy and I recently purchaced identical planes and He opted to use a TT Pro 61. I looked through his manual at the recomended prop size and it says 11x7...??? That is what I run on an OS .46 fx... Is the Pro 61 that weak? Or is this an error in the manual? I used to run a 12x6 on a bushinged OS .61 fp with no problems. I would think the Pro .61 should be able to comfortably spin an APC 14x4 (for 3D use) or a 12x6 like my old bushinged .60 at least. Does anyone have prior experience with this engine and might be able to offer some prop recomendations?

GarySS

My Feedback: (13)

I ran a 12x6 MasterAirscrew, I think, on mine. It produced pretty good power, but dang it wouldn't stay running very well below 1/2 throttle..........and I had engine experts look at it. So, it's long gone

rainedave

My Feedback: (1)

11x7 is the "traditional" prop typically used for breaking in high-revving sixties. My Tower .61 manual also recommends that prop for break in. A 12x6 is a similar load to an 11x7. But, it's better to use a smaller diameter/higher pitched prop like the 11x7 for break in since it revs high and blows a lot of air over the cylinder and head. After the engine is broken in you can use an 11x8 or 12x7, etc.

David

Cyclic Hardover

My Feedback: (3)

I mounted that engine and that prop on a 40 size p-51. Went like a b.o.o.h! Don't forget, props are also chosen by aircraft type, and style of flying. Recommended doesn't always work

Gungadin

Have run the TT61 Pro for many flights in two different airplanes and ran props including 12x6, 13x6, and 13x5. Liked it best with an Ultrathrust muffler which gave it a nice boost. Tried different carbs on it cause I did not like the stock version. With the carb from my Irvine 72 the TT61 pro runs great. Hard to beat in this mode. Just my experience.

Jazzy

Never had any carb probs with mine. Made my own inverted muffler for my Spit - original is heavy with a big ol' conical baffle in it. Spins an APC 13X7 very nicely! Don't quite remember what the R'ss were but I think they were around 11.5K to 12K.

"Weak?" Not compared to its copies and as respectable as it's little brother - the 46.

I have seen the plain bearing (bushing) version really crank out the R's at considerably less weight!

Mr67Stang

Thank you all for sharing your experiences with the engine. It is mounted on a very lightly built Extra 260. They recomend a .46 for the plane but you know what that means