Originally Posted by NoyGonnaDoIt

Another consideration - since this is a multi-engine airplane, the CFI must have a least 5 hours PIC time in make and model under 61.195(f). While it's not necessary to have the endorsement to log those 5 hours, those 5 hours should certainly be enough to get it.

That's the legality.

As others mentioned, safety is also a consideration, I'm not sure that it's such a good idea to be teaching in a 260 or 300 HP per engine twin when you haven't even been signed off to fly a simple 182. Certainly, in case of some kind of mishap, it would be interesting to hear the answer to the FAA's questions on that subject.