2002 F115TLRA idles great but stumbles on acceleration, any ideas?

[Baitboy2018]

Had the boat out yesterday and it ran fine for about 20 minutes then I noticed it was bogging down. Checked the fuel bulb and it was soft so I pumped it back up and the motor ran ok for a short time before doing it again. It eventually got to the point where it would only idle, try to accelerate and it would bog down and quit. I've checked the fuel filter, it has some water in it so I drained it and replaced the small filter, but it didn't cure the problem. I've ordered a new water/fuel separator filter in hopes that will cure the issue and remove any water that may be in the system. Is it possible the water in the system was enough to keep the motor from accelerating, but still be able to idle? This is my first 4 stroke so I'm not too familiar with the workings so any help would be greatly appreciated.

[rejesterd]

Yes, water in the fuel system is horrible and will cause performance issues.. but more importantly, it can really damage your engine internals. So don't run it again until you clean out the entire fuel system. That means out of the fuel tank, out of any hoses that go from the tank to the engine, the separator filter, the on-engine fuel filter, and the vapor separator.

If it were me, I would get a small portable tank and put about 2 gallons of fresh fuel in it. Then unhook the end of the bulb assembly hose that goes back to your fuel/water separator filter. Connect that end of the hose to your portable fuel tank. Then loosen the little brass drain screw at the bottom of the vapor separator after hooking up a tube/hose to the nipple on the bottom. The vapor separator is hidden behind the air intake, but if you look closely, you should find the screw & nipple. Then point the other end of the tube into a clear container, and start pumping the primer bulb. That should pump out almost all of the old fuel & water from the lines inside the engine. Once it's all out, replace the fuel filter again. Then see how it runs off the portable tank. If it's better, then you just have to clean out your main tank of all that old fuel/water, and replace your water separator filter again. I've never had to drain my fuel tank, so I'm not sure what the most practical way is. Someone here should have an idea though.

[pstephens46]

So you pumped the fuel bulb and performance improved? Did you try that again when it again started having problems? Water in filter does not mean there is water inside the motor.

[fairdeal]

Checked the fuel bulb and it was soft so I pumped it back up

That bit of information tells us almost nothing.
The bulb is supposed to be "soft" - its only "hard" if you squeeze it,
and then as soon as you stop squeezing and run the engine it gets "soft" again.

Now, as pstephens suggests,
if continuously squeezing the bulb, while the engine is running,
solves the 'issue' and the engine runs fine, then that tells us something useful.

'some' water in the fuel filter may or may not be related to your problem;
but the problem is almost certainly 'fuel related'.

'Flushing' the Vapor Separator Tank as suggested above is a good first step -
(collecting / examining what comes out may be informative)

Your issue may be a clogged screen in the VST,
requiring disassembly and cleaning -
and/or clogged injectors - which can be removed for professional service

[99yam40]

monitoring fuel pressures should point to some place to be looking for a problem

[Baitboy2018]

Thanks for the input, I'm draining and cleaning the entire fuel system today, Thursday, and replacing the water/fuel separator filter as well. What I still don't understand is why it ran so well for a while and then began to lose power? At worst the fuel in the tank is about 2 months old and I run high octane fuel just to prevent octane loss when it sits. I will admit though, I ran out of fuel stabilizer so did not put any in the tank of fuel currently in the boat. My bad I know.

[rejesterd]

What I still don't understand is why it ran so well for a while and then began to lose power?

I assume you're asking this because if the issue was stale fuel, it would likely not run well for the first 20 minutes like you observed. That's correct. However, 2 months is enough time for unstabilized fuel to cause performance problems.. and they can be random. So it's a hard question to answer with certainty. Another possibility is water got into your fuel tank. If you started your engine and disconnected the fuel line, it would idle for a good long while before it actually stalled out. The engine itself holds a lot of fuel. So it's possible that once that fuel in the engine (which wasn't contaminated with water) ran out, contaminated fuel from the tank started coming in. Again, it's a hard question to answer with certainty.

What is certain is: you have water in the system. Get it out first, then closely monitor the onboard fuel filter. If it happens again and you've stabilized the fuel, then you have a leak somewhere that's letting moisture the lines.

Also, how soft was the bulb when you noticed the issue? Ideally, once the system is primed, you shouldn't have to touch the bulb for a good long while. Even on the first startup in the spring, I don't have to pump my bulb. If you constantly have to pump it, that's another symptom of a leak somewhere.

[99yam40]

Thanks for the input, I'm draining and cleaning the entire fuel system today, Thursday, and replacing the water/fuel separator filter as well. What I still don't understand is why it ran so well for a while and then began to lose power? At worst the fuel in the tank is about 2 months old and I run high octane fuel just to prevent octane loss when it sits. I will admit though, I ran out of fuel stabilizer so did not put any in the tank of fuel currently in the boat. My bad I know.

what kind of fuel are you talking about?
if it was E fuel then any water in the tank will kill that fuel even if you put in stabilizer