It's weird you have issues with 5 of the 6 pumps! Is that correct. I have replaced 2. One just stoped working, the second must have froze b/c the housing was cracke. Both those pumps were the fill pumps for the rear tanks, closest to the transom. The other 4 pumps, more inboard, have been just fine. I have 2 spare pumps with me at all times. They are super easy to replace if you have the connectors already crimped for plug and play, if you know what I mean.
Sometimes the stock wiring can just become loose.