Al Jr.
Self bailing boats were an adaptation of the idea that trawler designers/builders used to bail the decks through holes ABOVE the waterline. These water outlets have a nautical name although it eludes me now. These holes can be seen from a distance on most trawlers from the easily recognized stains left from water and stuff flowing overboard. Modern rafts and now pleasure boats have the bailing holes usually at or above the waterline. Just like the trawler, they only work as a function of major positive bouyancy. Any significant loss of bouyancy and you know what happens. My guess is that these holes work due to the tremendous amounts of added bouyant foam injected into hulls these days with assistance of check vavles (water valve that allow water to flow only in one direction). My guess is that buying a self bailer is indeed the right choice. Your 71 Mastercraft would probably sink like a rock if she had holes in her and besides, you would never sleep a wink if you removed her bilge pump and that sage advice comes from experiencing several sleepless nights when my pump was out. Don't catch em all! Good luck and go get em!
Andy