I used to have a hayward 1 speed, 2HP pump for my 21' round above ground pool. It was causing issues with my filter/plumbing (leaks) because it's apparently oversized for the filter/pool. I've since purchased a replacement Hayward 1 speed, 1HP pump and when I go to turn it on it just humms and I have to smack it a few times in order for it to start working. Any ideas on why this would be or how I can fix it. The only thing I did was install the timer from the 2HP motor on to the new 1HP motor which is part of the aggravation. I can't really use the timer because when the timer turns it on it sits there and humms and no one is there to smack it!