I just inherited an 18K gallon in-ground gunite - our
first pool. The pool looks great thanks to the info
on this forum! The problem is that I think the pump
motor is dying. The in-pool jets aren't pushing much
water and the pump makes quite a racket. So I've
about decided to get a new motor (rebuild is ~$100
I've heard vs. ~$160 for a new one). My quandary is
what size motor to get. The original pool install
(1984) used a 1.5 hp Sta-Rite XL-VII pump (no specs
available). Then in 1994, this was replaced with a
Sta-Rite P4E6E-151L 1hp pump (high service factor).
Should I stick with a 1hp motor or try to fit a 1.5hp
motor on this pump? I've read that sizing a pump to
a pool is a bit of black magic - any way to estimate
what I need or should I just assume that whoever
switched from 1.5hp to 1hp knew what they were doing?

Some stats:
18K gunite w/ attached spa
Sta-Rite S7D75 DE filter (37sq ft)
two skimmers in pool
two main drains (one in pool & one in spa)
seven jets total (3 in pool & 4 in spa)
one "cleaning" jet (to attach my Ray-Vac)

Thanks in advance!