Hi bottomcat I would suggest a 150,000 BTU heater for your application as this size unit would give you a 30 degree temperature rise. The unit I like is the Raypak 014784 heater, this is a 150,000 BTU unit and in my experience has been very reliable. I would also highly recommend using a solar blanket when your pool is not in use as evaporation accounts for nearly 70% of the heat loss in your pool.