Another vote for the Tower .75.

I had 8 of these at one time. Sold off a few over the years. I still have 3 of them. Great engines. I have one on a highly modified LT-40 and fly it with a 13-6 prop. I had another on a 50 size 3DEdge 540 but the airframe finally wore out. That engine has a TONof fuel through it. It was mounted inverted and hooked up to a Cline regulator. The head is no longer purple but it's still got plenty of pinch at the top and it doesn't give me any trouble. The other was on a 50 size Giles 202 for about 15 flights and then I sold the airframe because it was too heavy for 3D at 6000 elevation.

Had one carb arm fall off a few years ago. The carb was ruined. I couldn't get the throttle arm attached back where it would stay on for an entire flight so that engine sat in a box for a LONGtime. Tower was out of stock on the parts for about a year and I finally got desperate for a new carb. Ed Mormon said he tried a carb from an SK .90 and it worked well. So I bought one. I had to take about 1/16" off the carb throat so it would seat down in the crankcase all the way and seal up. The carb throat on the SK is just a little longer than the stock Tower carb. But the diameter is the exact same. That engine runs even better than it did before. The SK carb seams to have a different taper on the needle and is much smoother in the mid range.

I did suck the front bearing cage out of one engine...... TWICE. The first time a little piece of the cage went past the crankshaft and ended up in the bottom of the crankcase under the connecting rod. It left a nasty gouge in the side of the case where it went all the way past the crank shaft before it found it's way to the bottom of the crankcase. I called Tower and they send me new bearings and a new crank shaft. I don't know why. I would have preferred a new case, but the parts were free so I was content to live with the gouge in the case. That same engine sucked the front bearing cage again about 5 gallons later. I sent it to Tower and they rebuilt it. Sent it back to me with LARGEmetal shavings in the case. Good thing I took it apart to inspect after their tech department rebuilt it and sent it back to me. I took that engine apart to clean it out good and lube it before running it again. I was gun shy about the bearings on that engine, so I decided to put Boca bearings in that engine and have not had a problem since. It's been run another 8 or 10 gallons of fuel since then and I don't notice any drop in power or reliability.

To my knowledge, I am one of just a handful of guys who have had bearing problems on the Tower .75. I think it was just a fluke or dumb luck that I shot the front bearing out of the same engine twice in under 6 gallons. Maybe the case isn't manufacturerd perfectly on that engine? The Boca bearings seam to have stopped the trouble and I consider it a reliable and powerful engine today. I certainly wouldn't shy away from the Tower engine based on one or two isolated reports of bearing failures.

Between the Tower and the OS, I'd take (2)Towers for the price of a single OS. The Tower .75 is on sale right now for $100 and the OScosts $210