Can someone tell me what rule of thumb is used with respect to weight when selecting an engine?

.049 -> 16oz
.060 -> ?

ect ...

Thanks in advance.

Marv

The weight depends on the wing area to carry it... if you put an 049 on a glider, it can mush around 32 oz. If you want a sport plane type performance, then 20-22 oz is a good max wt, better still 16 oz. Try to keep the wing loading below 16 oz/sf, and closer to 12oz/sf or even lower. Below 6 or 7 oz/sf you will start to have a fun plane that will fly happily very slow,,, , but then you cant deal with much wind with really light wing loads.
The power difference with an 061 isnt that significant... if it flies on an 061, chances are an 046 will also carry it acceptably.

my $.02 worth