25HP yamaha 2 stroke fuel problem

I'm having an issue lately with my 25 hp 2 stroke tiller drive. It's been going on off and on for several months now and I can't seem to find the problem. What's happening is the motor starts, idles, and runs great but then sometimes when making a long run, the motor will start to bog down as if it's not getting any fuel. I'll then reach back and pump the bulb, which doesn't seem to have any fuel in it, and she purs like a kitten again for a little while and then does the same thing again. This usually happens later on in the day after I've ran around the Bay for awhile. I do a lot of wade fishing so I'm moving around the bays a lot. Usually this happens to me on my return trip back to the dock. Some days when I'm out it doesn't happen at all. Last time I was out I had to pump the bulb several times just to make it back to the dock. I've replaced the gas hose along with a new gas tank and fitting and same thing happened. I think my next move is to try and replace the fuel pump on it unless anyone has any other thoughts. I've read about the gas lines mabe having an air leak but if this were the case I'd imagine I'd be having this issue a lot more frequently but then again I'm not mechanic.