Now that you have the old pump off you may be able to fix it and keep it as a spare. A friend had a similar issue and replaced his pump. He through the old one out. I decided to take it apart to see why it failed. It had a bit of sand in it. This caused the valves to leak water so it kept cycling. I washed it out and it works fine now. It did not cost anything to fix just 10 minutes of my time. It is now in my spares locker as he sold his boat.
Bob