Just got my 2007 Yamaha 150HP 4 stroke back from the shop. Needed the fuel pump replaced. The fuel filters (all of them) were covered and clogged in a black film. The mechanics said that all were replaced as well as the fuel pump which also had the black film inside it and caused the fuel pump to seize up. The film was also inside all fuel lines which he swabbed out.

This motor is 3 years old - it has never been idle for more than 2 weeks since I bought it new 3 years ago. I fish approximately 100 times per year so it gets plenty of exercise. No problems until this one. I have never used any additive in the gas and buy my gas from busy active stations. I use regular gas.

Has anyone any idea what could cause this?

I have ran into this problem and found that the black floats on the fuel tank sender was the problem floats were flaking off and getting into fuel system....OPTI

OPTI - thanks for the reply.

I will ask about this the next time I am at the shop. This black stuff looked different than any thing I have ever seen in gas or gas filters. Reminded me of toner like you use in copy machines when you wash it off your hands.

The parts he used on the job were fuel pump, 10 micron filter, filter element, float chamber gasket and another filter.

There is a possiblility that the alcohol in the fuel is deterating the fuel lines from the tank to the engine. I would check the inside of those fuel lines, by rubbing a swab in them and see if the material is breaking down.

Mike - good idea - as soon as I thaw out I will go to the boat shed and check it out.