70 hp VRO loading up

I have a 70 hp VRO '91 model that randomly loads up on me. When running properly is as strong of an engine for its size as I have seen. I don't idle excessively. I had a "tune up" last summer and I think all he did was change the plugs and there was no difference. It doesn't bog down all the time. I seem to notice if I leave my engine trimmed down (not all the way down, just below level) while not running or at idle it Boggs down more. Previously if I pumped the bulb to when it gets hard, it would randomly work properly. The times when I had trouble I suspected it wasnt getting enough fuel so I would squeeze the bulb to find it soft. With the cowling off and squeezing the bulb I could hear a siphoning noise coming from where the fuel pump is attached. Also, I could see fuel in my engine case and fuel in the water when I backed into the water. The mechanic said it just had fouled plugs and was getting too much fuel and drowning the plugs. To me, it seems like there is either a hole in the fuel pump or a bad diaphragm or gasket that when separated sucks air into the fuel system and gas into the lake from down the shaft housing.

Like I said, it happens at random but the last two trips out I was on plane and it bogged down. If I stop, rev the engine in neutral for a few seconds, it will take right back off. I guess I shouldn't have said loaded up because it's not like a carbed up engine, it's like it's not getting fuel.

Anyone have any insight? Bad diaphragm in fuel pump? Fixable? Replace pump?

Thank you very much for your help.

Allen