Randy:

Sounds like at least a part of your problem might be overheating with the 10x6 3b props. That's a whale of a load for those dinky little 0.25 engines. Try going down to 8" diameter for the 3b props. My two 0.25 engines, an MDS and a Magnum, are quite happy with the 8x6 3b props on them. The 10x6 3b is what I run on the Magnum XL 46 edngines.

Bill.