What would be the 4 stroke engine that would replace a 91 2 stroke?

In my case my YS 1.10 or my OS .91. In the last decade or so the difference between the two and four strokes has narrowed too much to bother with the old school thinking. The two stroke will always pull more and faster RPMs but the torque of the four stroke puts them about the same. I was running a SK .91 two stroke in an Extre 260 and changed that out with an OS .91 FS and other then a little top end speed the plane flew the same. Gene, keep in mind I only use the better makes of four strokes and the cheaper brand of two strokes. That makes a difference. The SK is a low RPM high torque two stroke engine, not a big RPM ball of fire. I also don't run Magnum four strokes. Only four strokes I have on hand at the moment are the YS and OS brands. Something to keep in mind.

depends some on the plane.  At least 120, up to 150.

Tom

WHAT!!!! Graybeard, you don't run magnum 4 strokes

I do have a .91 Magnum under the bench, it runs. I pulled it out of an old trainer and replaced it with an OS .91. Something I discovered, well, maybe I just never gave it any though? The Magnum header fits the OS and is cheaper. I didn't look but maybe the threads aren't cut in them as deep either?? If so I will buy a couple of there headers, the OS headers suck!!![:@][:@] Swallow!![&:]

What plane Gene?