2013 df115a surges at WOT

[Clarboy]

Hey guys, new here, hoping to get some help with this problem. My 115 starting losing power/rpms on me one day after 3 minutes leaving the ramp. It would suddenly accelerate then back down like I was throttling back. So I'm figuring time for new fuel filter/separator . Done that, made no difference. Well I'm thinking I'm getting air in the line somewhere or maybe primer bulb shot. Replaced primer, no difference. Humm, well I done vacuum testing on the lines and pressure testing, they ok, no leaks detected. Well, I read online about the check valve ball on the fuel pickup could be stuck. I done away with that completely, no obstruction there. I was thinking maybe not venting well from fuel tank, I removed the charcoal canister thingy, don't know what it's called but I gave good ventilation. Put a loop in hose going to vent so fuel won't spill out. Well, I'm thinking now bad fuel. And yes I have been using the cheap stuff e10 with some Stabile as it's difficult to find ethanol free where I live. So I pumped out all the fuel, replaced with good 90proof ethanol free, burnt the old fuel in my pickup truck, truck run fine. I also removed the inline filter that's just before the low pressure pump and put a pressure gauge on the fuel rail. Took it down the river for a test. It ran like a sweet dream, pressure about 40 to 43lb . Well, until you hit around 5500 rpm, she starts to stumble, like it's running out of fuel. I quickly look at the fuel pressure gauge, still pumping fine. I squezzed the primer bulb, it wasn't quite hard hard but not collapsed soft. Seem to improve some but would go back to the same thing. The dealer is 2 hours away, really don't want to pay the price either as if it's a fuel issue then it's on me. Don't imagine warranty covers that. I've ordered a new filter cartridge for the inline, new filters for Vapor blender thing, all new hoses coming from the tank, new spark plugs. I'd appreciate if anyone has advice for me on what to check next. Thanks

[artdf175]

You might try a small - say 5 gallon fuel tank that you can connect directly to the engine
Disconnect old fuel source and run dry then hook up the 5 gallon and after running 5 or 10 minutes see if the same problem surfaces
Just need at this point to rule out the fuel tank and hoses
The E10 stuff will do bad things to the inside of the fuel hose as well and not obvious
You might see some gunk in the inline fuel filter pre low pressure fuel pump
The inner wall may have or being broken down and limit fuel flow as well
Art

[Clarboy]

Thanks for the reply, I guess there's really no smoking gun as I was hoping for. I do have $180 worth of parts and filters coming to try. Also new fuel hoses from tank to filter to primer. The fuel lines on the engine itself are crazy priced. Do they break down as well ? Wondering if I could substitute these lines with the Sierra grey hoses that more ethanol friendly. Which is what I'm doing in the boat.