Fuel Starvation in 2016 Yamaha 150 problem.

[courymic]

Purchased a 2016 boat with a Yamaha 150 on it with 20 hrs. Since ownership, I've gotten some intermittent power loss only under high RPMs. Once the symptoms occur( full power loss/surging until I return to idle or low rpm), the problem doesn't go away until remedied. I've tried several things to solve and am out of ideas on what to try. Things I've tried... Cleaned the VST tank, fuel injectors, changed all filters and Fuel/WWater Sep.. Drained fuel tank, checked the fuel vent was clear. The biggest thing I can offer is that the "solution" which causes the symptoms to go away for up to 3-5 hours of run time is If I simply loosen the fuel filter cup and retighten it, the engine returns to normal. There is a noticeable change in the amount of fuel in the cup once I've "broken" the seal. My best guess is air is getting in the line further up, that assembly isn't working properly, or a fuel flow issue further up the line. Does anyone know what the electrical line running off the bottom of the fuel filter cup is for? I'm wondering if there is a faulty issue in there and its sensing incorrectly and shutting the engine down. Clearly, I'm reaching. Thanks for all the advice in advance.

[fairdeal]

the wire connector at the bottom of the filter bowl is a "water in fuel" detector switch

if water collects in the bowl high enough to trip the switch,
you will get a visual indication on your gauge and audible alarm

but it doesn't affect how the engine runs

[99yam40]

Purchased a 2016 boat with a Yamaha 150 on it with 20 hrs. Since ownership, I've gotten some intermittent power loss only under high RPMs. Once the symptoms occur( full power loss/surging until I return to idle or low rpm), the problem doesn't go away until remedied. I've tried several things to solve and am out of ideas on what to try. Things I've tried... Cleaned the VST tank, fuel injectors, changed all filters and Fuel/WWater Sep.. Drained fuel tank, checked the fuel vent was clear. The biggest thing I can offer is that the "solution" which causes the symptoms to go away for up to 3-5 hours of run time is If I simply loosen the fuel filter cup and retighten it, the engine returns to normal. There is a noticeable change in the amount of fuel in the cup once I've "broken" the seal. My best guess is air is getting in the line further up, that assembly isn't working properly, or a fuel flow issue further up the line. Does anyone know what the electrical line running off the bottom of the fuel filter cup is for? I'm wondering if there is a faulty issue in there and its sensing incorrectly and shutting the engine down. Clearly, I'm reaching. Thanks for all the advice in advance.

Have you tried changing the o ring seal on the filter cup you undo and reseat to make it Ok for a little while.

or replace that whole unit

[boscoe99]

the wire connector at the bottom of the filter bowl is a "water in fuel" detector switch

if water collects in the bowl high enough to trip the switch,
you will get a visual indication on your gauge and audible alarm

but it doesn't affect how the engine runs

It should be noted that the visual alarm will only be seen on a Command Link gauge. Not on an analog gauge or the conventional multi-function tachometer.

The alarm will only be heard when the motor is in neutral. The alarm will be an intermittent beeping tone as opposed to the normal steady alarm tone that is heard due to over temperature or low oil pressure.

[rodbolt17]

And there again, a Yamaha is not every Yamaha.
my F150 gives a steady tone if the water detect triggers,

[99yam40]

But what do you(Rod and Boscoe) think his problem is with the intermittent power loss only under high RPMs that goes away for a few hours when he reseats the filter bowl?
the seal the cup itself, or something totally different?

[boscoe99]

And there again, a Yamaha is not every Yamaha.
my F150 gives a steady tone if the water detect triggers,

In neutral or in gear? What model year do you have?

[boscoe99]

But what do you(Rod and Boscoe) think his problem is with the intermittent power loss only under high RPMs that goes away for a few hours when he reseats the filter bowl?
the seal the cup itself, or something totally different?

Appears to be fuel related. Without monitoring vacuum in the supply side of the system and pressure in the output side of the system he is splatter gunning.

[courymic]

Thanks for the responses so far. Thanks for the clarification on the purpose of the wire. I'm not receiving any errors however on the gagues but glad I know what its for now. I have replaced the fuel filter itself several times part(6) in the exploded diagram. The problem only occurs when in gear and the symptoms only occur under a high load... when the fuel flow reaches around 7GPH which I can't replicate that in neutral. Due to this, I cannot replicate the problem or test by running on a separate tank on the muffs. I have not replaced the entire fuel filter cup system as of yet, the problem seems to exist higher up the line either causing a vacuum that I am clear when I loosen the fuel filter cup. The engine is a 2016 150. I dont have the model number here but will post it when next out to the boat this week. I had someone mention that there is a check valve on the outflowing side of the gas tank that can get clogged up and may be causing some vacuum fuel flow issues further down the line. Its worth noting that during the engine symptoms the primer bulb is normal and pumping it has no effect on the engine.

[courymic]

I know we are somewhat "splatter gunning". I could obviously just pay a grand and have a mechanic go searching. I enjoy trying to solve these things independently when able. Thanks for all the ideas here!

[99yam40]

I would do as I said before replace the o ring 1st to see if that helps and then the whole filter cup or assembly.
sounds to me like it is sucking air at the place you change things when reseating the cup

[courymic]

Ill try replacing the ring and the onboard marine tank venting test this week and report back. Ive put compressed air through the fuel vent on the side of the boat to confirm a clear path to the tank, which it is free and clear. Thanks again.

[rodbolt17]

why not simply monitor fuel line vacume and rail pressure?
womt cost a grand and will narrow why the rail is losing pressure.