I had a similar issue with my F115, would just run fine then cut. Squeeze it up again, off you go for a while. Have you looked at the little filter mounted on the motor under the cowling when this happens? It will be showing an air space up top if you have an air leak. I went mad trying to find mine-even pulled the pickups out of the tote tanks and refixed them. Turned out there was a dodgy joiner between the section of fuel line from the motor, and the line to the tote tanks, hidden inside the split flex conduit that all the cables, lines and controls were run in. It won't necessarily leak fuel out, but it will suck air in. 

HTH

 Easy way to check if it is a blocked breather is to loosen the fuel tank cap so air can get into the tank as fuel is used. 

 Looking forward to answer, had the same thing on the weekend. Did 25nm without issue, got to spot n went for dive. Ready to leave, go to throttle down and it splurts n sounds horrid n dies. Starts again, dies n rinse n repeat. Got it out of the wind n had more of the same where it would idle ok and then after 15mins whilst idling. Figured it out n primed the bulb exactly like crabking, got it up to 20 knots in rough conditions n ran fine for 45 mins and then back to low forward it dies. Rinse n repeat with dying n starting n pumping bulb in low revs until the throttles. 

Havent had a good look at fuel line or filter yet, but is on this weeks todo list.

 Same  thing happened to me ,ran fine for whole week. Took it out again Had to pump fuel bulb to get me home. Ended up finding water in fuel and gunk in carbies.

Very similar issues on weekend also....mine running normal mid range but dying high end load and spurting at lower end.

Will pull Fuel lines and carbies during week to clean....check for leaks / blockage.

 Changed plugs and water separation  filter , cleaned little filter on motor and it kept stalling on low speed.started to run it on 95 instead of 91, problem sorted so far.

 What motor is it.  If its a yamaha 4 stroke the fuel filter under the cowling are notorious for getting a hairline crack in the plastic housing. You wont see it but can usually smell a faint waft of petrol fumes when you take the cover off. Did my head in for months it was that smaller leak.  Its a jaw dropping price for a new one.  Another thing is the Water seperator filter can get fully clogged .  What happens is it cloggs up and wont let fuel through. Then a chunk of the shit on the filter paper falls off and lets fuel through for a while. It sucks so much harder than normal and air will go through joins it usually wouldnt.  You also need proper thread sealer on the joins on the water seperator filter  and fuel tank like loxeal 58.11  if its all metal fittings not teflon tape.