C-22's should not need bilge pumps
You are applying the wrong effort to your leakage problems.Quite simply, if something is leaking on a C-22, it needs to be repaired at the source, as opposed to installing a device that a C-22 should not require.Regarding the lock down bolt, usually just some heavy marine grade grease on the threads will prevent water seepage there. Other than that, you have leaks from deck attachments, windows, and hatches all which require either rebedding with a good marine grade silicone or some gasket needs to be replaced.Further, if you just take a look at the way a Catalina 22 is constructed, you will find there is no real bilge, just many separate compartments attached to the hull all of which would then require their own bilge pump.So then not only is it a matter of what bilge pump but how many.So, skip putting in a bilge pump, keep a regular watch on your boat, and be relentless about correcting leaks.