I've flown this plane on an OS 40 FP and for training purposes the power was perfect. That's a plain bearing engine that weighs under 12 oz with muffler. Light weight, super reliable, no bearings to rust, just the right power. The crazy thing is, no one seems to make an engine like this anymore. A couple of years ago you'd have your choice of an OS 46 LA or a TT 42 GP, either of which was similar in weight and reliability to the old 40 FP, but they are both discontinued now. You can still pick them up from individuals.

People now will tell you to get a ball bearing 46 with twice the power and 5 oz more weight. I think it's a bad idea for a trainer, because the throttle response is too much, the extra weight does you no good, and you've got ball bearings to take care of. I would pick up an OS 40 FP, 46 LA, or TT 42 GP in new condition from someone. There are thousands still around, and mostly unused. But most people will advise you to get the more powerful engine and tell you "that's what the throttle is for".

The OS 61s are likely very good engines, depending on condition, but they are too big, powerful and heavy for a trainer that size.

Jim