I've got a bad motor (smoking when running) and am ready to order up a new motor and stick it on the existing pump (see sig below.) It seems as if this would be a good opportunity to upgrade to a bigger motor, as there was once a 1.5 HP pump installed before we (possibly wrongly) put a new pump with a smaller (1 HP) motor in last year.

Just curious how one would calculate how much power a motor would need for a given size pool? I've got a 26,000 gallon in ground rectangular pool, with an outlet to the pool in the shallow end, a skimmer in the middle, and a return port in the deep end (all piped together with 1 1/2" PVC.)