i have a 2nd gen 2.0 si and was wondering if any other motors swap right in, without replacing mounts? like a b20 off the 3rd gen or a b16/17/18?

 

nope no direct swaps.

the 2.0 FI motor is a good motor though. no VTEC, but good nonetheless.

 

Nope, you are pretty much stuck with that. Start researching some turbo options and go that route.

 

A-series engines are iron blocks so they hold up to boost pretty good. As for swaps, the 3g b20a3 and a5 have different mount locations. There is, however, the jdm b20a that came in the jdm Prelude XXi and some Accords. The two b20s are identical to eachother except for the mounts and the trannies. Oddly, the early b20a's tranny looked more like one from an a-series engine. Honda claimed horsepower to be about 135hp

You'll find more info here:
http://3geez.com/showthread.php?threadid=86
http://people.clemson.edu/~summerr/2gsite/