There have been a lot of issues with fuel delivery, and not necessarily from the pump, but (also) from the tank. The bottom of old tanks can collect water and dust from the years, and this junk can clog the outlet port from the tank, and it can build up and clog at the shutoff valves too. It can totally clog the main filters with all sorts of stuff.
The fuel pump may be weak or failing, yes. All of these issues are routing maintenance on a boat anyway, so checking any of them won't hurt. Sooner or later all of them probably come into play in an old boat.
My main filters were so dirty I was surprised any fuel was actually getting through.
Carb float valves can act up, jets can clog, etc. It never hurts to run some carb cleaner through them
The ignition, however, is a MAJOR source of problems on these old boats, from my experience. I could never get mine running right until I finally switched to electronic. I had my distributors rebuilt at Mallory too, and the aftermarket points and rotors were so poor in quality, the rotor rubbed the underside of the crab cap.
Ballast resistors that have been removed can cause problems.
Faulty ignition switches and grounds can cause problems, make sure your motor is grounded properly at the battery and to the block.
Improperly adjusted valves can cause driving problems. Too tight and the motor won't idle down and top performance is poor too.
Timing must be done with a strobe. Any other way just won't work, in my experience.
Here is a relevant thread.
http://www.network54.com/Forum/message?forumid=424840&messageid=1123099503
Good luck! Once you find the culprit, the motors should run just fine if they did recently before. Mechanical type issues rarely manifest themselves like the symptoms you've described.
regards, Paul