2005 yamaha 115 problem

[tug]

My motor has 540 hours, runs fine for a bit then start surging, as in loosing power. Have replaced fuel lines ,filters,pump, antisiphone valve, pressure bulb, injectors cleaned vacuume pressure tank.cleaned fuel tank.
Any ideas
Thanks

 

[Efx]

There are two fuel pumps. Low pressure ( mechanical) and high pressure. I would look at the high presure pump inside the vst tank. Clean the tank well and measure the fuel presure at the fuel rail. Also, are the injectors seated well?

 

[afitzray]

Surging at idle also? Or only at mid to high rpm?

That's a tough one since it sounds like you've worked on everything between the tank and the injectors. You double checked all those connections that were just worked on to make sure air isn't getting in the fuel line somewhere? You could rule that out by temporarily adding a clear line right before the engine fuel filter just to make sure there's no bubbles in the fuel on the way in.

Checked your vent lines for kinked line, or debris (wasp nest etc) in the vent port on the hull?

Has someone already run the Yamaha diagnostic software to see if any sensors etc are showing errors?

 

[afitzray]

One more thing. Did you remove the pick up lines to inspect them when you were replacing parts? Sometimes they have a screen on the bottom that can clog, although it seems most don't have the screen. And sometimes they just degrade over time to the point that they could warp and restrict flow.

 

[camron]

My motor has 540 hours, runs fine for a bit then start surging, as in loosing power. Have replaced fuel lines ,filters,pump, antisiphone valve, pressure bulb, injectors cleaned vacuume pressure tank.cleaned fuel tank.
Any ideas
Thanks

Did you replace the vst filter as well?

 

[Antidote]

Look at your spark plugs. They will tell you if you're dropping a cylinder or two. If your plugs look like these then you know where to start. That injector, that spark plug, or that coil wire. If two plugs look bad it's that coil. If the plugs are all the same, then look at the entire fuel system (as you have done), the entire ignition system or the dreaded bad ground.