Larry, You might want to try the Rule RM-2000. It uses the magic water sensor which can't be jammed by debris. Of course the pump can still be jammed.
Here is a description of the switching system.
"no Float Switch Required. The Rule Mate series of
Bilge pumps feature a solid state water sensing
technology that eliminates the need for a separate
fl oat switch.
When water enters the bilge and reaches a certain height
(70mm) 2.", a sensor turns the pump on. After the water
is pumped out, another sensor shuts the pump off. The
sensor’s unique “field effect” technology is eco-friendly
because they only sense the dielectric constant of water.
In the event of an onboard oil spill, straight motor oil that
enters the bilge will not turn the pump on. Please note, that
this is not an oil overspill system or a safety measure device."