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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3342
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I am working on a 2006 Yamaha 115 HP Four stroke that has a

Customer Question

Hello
I am working on a 2006 Yamaha 115 HP Four stroke that has a low power problem. Just about the entire fuel system has been gone through or replaced. Already checked the fuel filter and fuel hoses on the boat side. Ran the engine on a separate fuel tank. The engine was checked out by the Yamaha Dealer here in Hawaii. The fuel rails were apparently cleaned and the invoice indicates that 3 of the injectors showed bad spray patterns so they were cleaned. Also one injector was replaced as it was leaking. The VST was taken apart too to check and it was ok.
So today I went to the boat and checked the pressure on the high pressure fuel and it was fine at 37 psi. The low pressure fuel pump was also replaced I need to tell you. This problem first started over a year ago and has steadily become worse and worse. Today the engine could barely reach 4000 rpm and this very light aluminum boat could only go at 11 mph. Owner says that it used to be able to reach over 5200 RPM before and reach well over 35 MPH.
Today I checked to see if all of the cylinders were firing electrically by using a timing light and clamping it over each spark plug wire while the engine was raised to full throttle. All cylinders appeared to be firing fine. Also need to tell you that the compression was tested many times and checked out well and the spark plugs are new.I can't think of anything else to do now as it seems like everything has been already done. Do you have any ideas what could be causing this low power problem? I even went on to verify that the throttle cable is advancing the throttle linkage to WOT. Now I'm stumped. The model number is ***** and the year code is 68V. Any ideas would be helpful Thank you
Alan
Submitted: 11 months ago.
Category: Boat
Expert:  Charles replied 11 months ago.

Hello, my name is***** will assist you.

I ran into a problem sort of like this in my shop. After doing much testing and cleaning, I pulled the filters from the injectors and corrected the problem. If the filters were replaced when the injectors were cleaned, they could be too small of a micron to allow proper fuel flow.

Customer: replied 11 months ago.
Thank you Charles for helping me with this problem. Unfortunately I'm not very familiar with this Yamaha Outboard. From the invoice, I see that the dealer did replace a couple of fuel filters but not sure if these are the ones you are referring to. Are there individual filters for each injector? And where are they located? I will send the part numbers of the filters to you. Thank you for your help
Expert:  Charles replied 11 months ago.

The filters that they replaced are not inside the injectors. They are in the fuel line and inside the VST.

To remove the injector filters, you will first need to pull the injectors.

Customer: replied 11 months ago.
Can you give me any tips on replacing these filters and would be extremely helpful if you could provide me with the part numbers of these filters so I can order them. Thanks so much Charles.
Expert:  Charles replied 11 months ago.

Run with them out. They are a special filter just for fuel injectors, I have removed many and never have had an issue.

Expert:  Charles replied 11 months ago.

turn a small wood screw into the fuel rail end of the injector, then use a pair of side cutters to wiggle the screw and filter out. Then reinstall the injectors.

Customer: replied 11 months ago.
Ok. What do you mean by Run with them out? Sorry.
Customer: replied 11 months ago.
Charles. Could you do me a big favor and provide me with the part number for those injector filters?
Thank you.
Expert:  Charles replied 11 months ago.

There is not a place that i can get the part number for that filter. Run with them out means just remove the filters and then reinstall the injectors. You will not harm anything. There are 3 filters before the fuel gets to the filters.

Customer: replied 11 months ago.
Ok. It makes sense as they only will cause future problems. Thanks so much.
Expert:  Charles replied 11 months ago.

Your very welcome.

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