I just picked up a like new pumped OS 91 four stroke for $100 minus the muffler.

Then engine was used once, crashed and repaired to like new condition. I borrowed a muffler from a new non pumped 91FS I purchased recently and tested the engine and it runs great.

Only problem is I just looked up the price of a new muffler and it's like $65 from Tower. Anyone have an idea where I might get a less expensive alternative?

Look at a magnum muffler for that same size engine. They are usually interchangable. HobbyPeople sells them.

Don

Yep, Magnum mufflers are a lot cheaper.

Thanks, guys, if I can't find one at the next couple swap meets I go to I'll purchase one of these Magnum Mufflers.

Any idea if they'd be less efficient at muffling the sound than the stock OS muffler? Our club has a strict sound policy.

I bought a magnum muffler for my os 91 after @ 20 flights it separted in air, the last part where it reduces down to the small tube is just pressed in to the bell, hence no back pressure and the engine rpm dropped , luckily I made it back to the field, I put it back together with jb weld and 2 screws , but ran across a os muffler in the mean time.......

I use the stock mufflers on mine most the time but I do have some headers with flex pipe welded onto them. There isn't any great noise problem even running a straight pipe. Four strokes are very quiet and don't require a muffler if it is a pumper. I do have one pipe set up with a pressure nipple and it works just fine. I have aquired a number of four stroke mufflers over the years from older engines and the shapes and sizes have changed a lot so a cheaper muffler like a magnum should work as well as any. If you can find an RC Report magazine published in Janurary of 09Brian Winch did a very good write up about four stroke mufflers, well worth the search.

you might check out the Turbo Header mufflers http://rcspecialties.net/ (sold here on RCU also).
I had a similar dilemma with a saito 150 and have been very happy with two of these mufflers (other one on a Saito 91).
Not super cheap, but they're well made and they are good people to deal with.
Good luck!