Took the boat out and it ran good for a while then just died and wouldn't start. Had to use the trolling motor to get in and load the boat. Got home popped the top off checked stuff out and there is air bubbles and a lot of them in the clear fuel line going from the diaphragm to the carbs. I'm stumped and need some advice. What is the problem. Also on the fuel bulb when I build pressure and fill fuel line is the bulb supposed to depress and kinda deflate? Help me please.