Engine stalls out when running wide open

[Mr.nitrox]

My 2000, 115hp yamaha is only getting to around 4000rpm wide open to start with. Then after staying wide open for a few minutes it stalls out due to gas flow (the primer ball is empty). There is plenty of gas, the filter is clean, it runs for hours with no stalling if I stay around 3500 rpms.
Any help would be much appreciated

[DennisG01]

Things to check:

-- Bad primer bulb (obviously)
-- Failing gas line (internally... ethanol can make this worse) between bulb and tank
-- Clogged pickup tube in tank
-- Clogged fuel vent. Visually check and/or run with fuel fill cap off to verify

Am I missing anything?

[fairdeal]

I'm having trouble imagining a primer bulb that is "empty"

although I'm sure the OP means empty of gas.

"Sucked flat" of course is the sign of a restriction "on the inlet side" whilst the engine fuel pump is functioning properly.

I suppose an air leak "on the inlet side" or cracked rubber of the bulb itself could result in an "empty" bulb.

[99yam40]

sucking air anywhere from bulb to tank pick up

[Mr.nitrox]

Thanks for the responeses
-I mean after stalling the bulb is empty of gas (not flat, its still inflated) just i have to squeeze it several times to fill bulb again.

-the bulb and whole fuel filter assembly are only a few months old

-nothing but non- E gas has been run through this outboard

DennisG01: the fuel vent is not visually clogged. But as far as the gas tank lid idea, To test this idea you're saying I should get plane and run wide open with the gas lid off and see if it doesn't stall?
And I will check to see if it's a clogged pickup tube in tank or try and see if its sacking air from somewhere when I get a chance, hopefully this after noon. I'm not exactly sure how to either of those but I've got a couple ideas I'm sure I can figure it out

[99yam40]

this past week my brother had a problem all of a sudden out in the bay with his C60 running out of fuel.Had to pump the bulb constantly to get back to ramp.

I told him to look for where it was sucking air or a bad fuel pump.

Turns out the plastic filter cup on motor was loose,he tightened it up and it runs fine now.

OP might check that filter and o ring also
look any where from pump back to tank
Check the pumps

[fairdeal]

I mean after stalling the bulb is empty of gas (not flat, its still inflated) just i have to squeeze it several times to fill bulb again.

hmmm.

When you say "to fill (the) bulb again"
you mean, until the bulb feels "hard"?

The bulb is a pump,
when you squeeze, you are pushing whatever is in it - air or fuel -
toward the engine.

Only after you have filled the carb bowl/VST (whichever you have) with fuel

will the bulb feel "full / hard".

Now the question is, when you've stalled out, and you squeeze the bulb -

are you pumping fuel - because the engine fuel pump has not been keeping up?

or are you pumping air - because the "prime" has been broken back to the tank?

[DennisG01]

Thanks for the responeses
-I mean after stalling the bulb is empty of gas (not flat, its still inflated) just i have to squeeze it several times to fill bulb again.

-the bulb and whole fuel filter assembly are only a few months old

-nothing but non- E gas has been run through this outboard

DennisG01: the fuel vent is not visually clogged. But as far as the gas tank lid idea, To test this idea you're saying I should get plane and run wide open with the gas lid off and see if it doesn't stall?
And I will check to see if it's a clogged pickup tube in tank or try and see if its sacking air from somewhere when I get a chance, hopefully this after noon. I'm not exactly sure how to either of those but I've got a couple ideas I'm sure I can figure it out

Yes, run with gas lid off. Obviously don't do it if it's choppy/windy and there's a chance of getting water splashed in there. But that will vent the tank.

BUT, in light of you further clarifying that the bulb was not flat, I'm thinking less of a restriction and more along the lines of air getting in the lines. Check the hose and the fittings on the way to the tank - for looseness and cracks/pinholes.

There's still a possibility of the pickup tube being cracked, but... will the issue happen every time you go WOT? Or is it only after the tank is no longer "full"?

Another easy test: Run with the engine cover/hood off and watch the small gas container on the port side (somewhat clear, with the red ring in it). It should stay about 1/2 to 2/3 full at all times. Or, at least, I assume you have one of those like my engine. Although it's probably only going to tell you what you already know.

To eliminate the tank side of this equation... hook up a 6-gallon gas tank to the fuel filter (boat side). If everything run good that way, th issue is from filter back. If you still have a problem, the issue is from the filter forward.

Also... don't assume that a relatively new gas bulb is good. Even brand new things can fail.

[cpostis]

My 2000, 115hp yamaha is only getting to around 4000rpm wide open to start with. Then after staying wide open for a few minutes it stalls out due to gas flow (the primer ball is empty). There is plenty of gas, the filter is clean, it runs for hours with no stalling if I stay around 3500 rpms.
Any help would be much appreciated

Please post your complete model #, for example F115TXRY, etc.
Do you have a VST? I ask because your symptoms are exactly what I had in my motor and it was a clogged VST filter (inside the VST tank, mounted on the high pressure pump.

Let us know.