It's possible to put an electric motor on your Seamaster. It won't be cheap, though. You'll have to put a good size brushless motor on there if you want it to perform well. At this size of airplane, the difference between brushed and brushless cost isn't all that much, especially after you wear out one or two brushed motors at $50 a pop, and the benefits of brushless (better efficiency) will make the extra money worthwhile.

If you have room for a 12" prop, here's the system I'd recommend: AXi 4120/14, 12x8 APC Thin Electric series prop, Castle Creations Phoenix 45 controller, and 16 Sanyo HR4/5FAUP cells. All the numbers make it look like a fairly light, moderately-priced, drop-in for a .46 2-stroke.