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 (until now) 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 black film?

Yes, by not using ring free and not changing filters soon enough. Also, ethonol. Hopefully the shop upgraded your pump and everything else with the new ones that were made to handle ethonol. I was also told not to use non ethenol gas once you have introduced ethenol gas into the boat as it makes the buildup stick better.

Thanks for the reply.

They installed a 10 micron filter and I bought the additive to add to the gas. Hopefully this will correct the problem. That black stuff was something that I had never seen in gas lines or filters before. Looked like copier toner looks when you wash it off of your hands - liquified soot.

I would change those filters atleast once every 2 years. Expensive but it will keep you on the water without problems.