99 opti air pump

[nautigator]

I have a pair of 150 opti's. I had an air pump fail on the Port motor last month, and now the Starboard one has broke. The crank/rod assembly let loose on both of them, causing holes in the body of the pump. I took the one in stride, but I am wondering if there is something I am doing to make them break. I do not over rev the motors, usually run at 4000 if the conditions allow.
(Aside from a few times the boat left the water in rough conditions) The pumps had oil in the crank cavity, so I don't think lack of oil is the issue. Any thoughts and advice would help.