The scientific method is rule based. Therefore, if there is not a significant overlap between the consequentialist and deontologist approaches, then consequentialism must be non-scientific.

And if a consequentialist is non-scientific, then how can she reliability predict consequences and thus know what is the ethical or moral thing to do?

Before anyone replies to this could you please confirm whether you are actually trying to make a serious point or if you are just trying to be facetious? You are conflating issues all over the place in ways that don't really seem to make sense.