I bought the mark 5 version. Repair kit cost a lot and I could only use the diaphragm. When the other parts failed I wouldn't be able to fix it, so I just went ahead and gave in to the inevitable and replaced it.

hello -
i saw your post about the MHK bilge pump, and i may have the same problem - it doesn't pump, so i probably need to rebuild it (or service it, at least). i turned the flaps (check valves) around, so they close now - yet it still wouldn't prime, must be a problem with the diaphragm. did you ever resolve the issue? i know it's been a couple of years, but maybe you remember.
thank you!
anton