f115 mechanical fuel pump

[skipjackrock]

I have a 2003 115 4 stroke that has had repeat fuel system problems. I cleaned the tank, replaced the fuel filters including a 10-micron water separator, replaced the fuel lines and replaced the failed electric pump. The engine ran fine for about three months. Now it looses power & stalls occaisionally at idle. I took the fuel system back apart and found alarge amount of black rubber residue inside the VST tank. I then checked what I forgot to check before-- the mechanical pump! Sure enough the pump diaphragm is disintegrating....
My question is does anybody know if Yamaha has changed the rubber formulation of the pump or will a new one do the same thing? The rubber cushion around the electric pump is swollen also. Thanks for your help- Jerry

 

[rodbolt]

Re: f115 mechanical fuel pump

welcome to ethanol fuels.
now 4 congressmen have introduced a bill to increase it from 10% to 15%.
however getting back to your problem.
with E fuels ALL rubber parts on the engine will have a shorter life span and WILL need to be replaced every few years.
its just how Alcohol works.