Had a similar problem. I would come back to the boat after it sat dormant, maybe an hour or two and the primer balls were flat. It sounds like you are losing prime. Check connections for an air leak. Maybe a leak around a seal on the separator/fuel filter(s), hose clamps or brass threads at the tank pick up. Temporary installation of some clear fuel line will show air bubbles and might reveal something. Also make sure to have the primer bulb as level as possible at rest or better yet elevated discharge side up. this allows air to be more readily purged. Confirm that the primer ball is installed correctly, ie check the direction of fuel flow to the arrow on the ball. Hope this helps.