Yamaha 40 TLR vibration/missing at low RPM

My 20006 Yamaha 40 TLR started to vibrate while just in gear and in a slow zone. I felt the fuel bulb and it was not very hard. After I squeezed it the motor started to run fine. It seems that there might have been only 1 or 2 cyl getting fuel and firing that caused the vibration. It also started to cut out. It ran fine after I squeezed the bulb a few times. I then had it up to 5200 RPM with no problem. I have a water separator filter in the fuel line before the bulb.
What would cause the bulb to be soft? Could it be the fuel pump or just clogged fuel line or carbs? I would guess that there is about 75 to 100 hours max on the motor. The gas tank is mounted in the front of the boat
(2000 15T Pathfinder) and the fuel line is about 13 feet long.

Re: Yamaha 40 TLR vibration/missing at low RPM

It will not stay completly firm but that fuel line is long

Re: Yamaha 40 TLR vibration/missing at low RPM

If it's running fine at WOT and not when at lower rpm's, I would look into the fuel pump.
Also,consider trying an auxiliary fuel tank.

Re: Yamaha 40 TLR vibration/missing at low RPM

The tank that is in the boat is the factory installed 17gal. fiberglass tank.

I replaced the fuel line from the tank to the motor and checked the pickup in the tank.