In California if you're replacing a pool pump you only have 2 choices, less then 1Hp or variable speed
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If your not heating the pool water a few hours a day is fine. Maintain a chlorine level in the pool. As far as how late you can keep it open all depends on the weather but I wouldn't push it much more then Thanksgiving. What town are you in??
Greg
Try pouring water over each connection one at a time. The water will get sucked in if there is a leak and the air in the pump should stop for a few seconds. You might also be able to hear the air and water being sucked in. Also check the pump drain plug
Thats a good price. I would look at the overall condition of the heater, the bottom is most likely rotted. If it is you'd be better off replacing the whole thing. A replacement Raypak 335k is about $3300 installed