2006 F250TXR possible fuel problem

[Grumpy_one]

Sorry if this gets double posted, not sure what happened to first post. I saw something about it being possible spam, if it does pop up, I'll delete it. But it went something like this:

I'm posting a video of what I'm experiencing in the boat. I've been convinced that's is a fuel starvation issue until today someone mentioned "safemode". Didn't know these outboards had such a thing. Symptoms: will run fine at 4000rpm all day long. Once it's been at 4000rpm for awhile and try to go to WOT or 6000rpm, it dies or stutters. If I let it idle for awhile and go to WOT, I'll be able to hold 6000rpm for about 57 seconds before it stutters and I throw it into idle, but doesn't die. Actions: changed VST filter, fuel filter, and water/fuel separator, no help. I had my wife watch the fuel bowl during the event, says it never changed when engine stuttered. I'll call a stutter because at some point when it dies off of 6000rpm, it seems to have a bump before completely dying out suggesting that it's starving for fuel and not going into "safemode". This guy wants to charge me 110.00 to hook up diagnostics and see if the motor is going into safemode or has any codes showing. Where can I get one of these diagnostic tools? expensive?

Question 1: if the low pressure pump is falling, will the motor self prime the VST at 4000rpm? or at all? I understand the 10/20 second on/off below 1200 rpm.

Question 2: if the high pressure pump is failing, will the motor run at all?

Question 3: is there a diagram/chart of where I can be monitoring pressures during engine run? i.e. which fuel lines to tee into, what pressure to be reading? at idle, at full throttle

Question 4: how do I verify the check valve at the VST? From other postings, I see it operates at 10psi. a) is this a viable solution to my problem?

Video:https://www.youtube.com/watch?v=Gm4_TrNQcDU

Actions not completed: have not verified bulb fills VST during event.

[fairdeal]

"safemode" - if Yamaha uses that term (I don't recall)
would refer to rpm reduction for high temperature, or low oil pressure
you would get a warning horn, and an indication on the tach or CL gauge.

now, that engine also may have a "over-rev in neutral" control -
which would cause rpm reduction somewhere over 4,000 rpm
IF the switch were defective
and YDS would be helpful for seeing that -
(btw, if you want the diagnostic software/cable,
you can find it on eBay for ~$60)

but it seems you are describing a fuel problem
i.e. the HP fuel pump is not supplying the fuel rail at WOT
probably because the VST is running empty

the faster to rpms under load, the greater the fuel demand-
its certainly plausible - for various reasons -
that the VST is kept full at lower rpms
but not at or close to WOT


could easily be the LP pump itself is fine, but hamstrung by something else


some models has a handy Schrader valve on the rail to attach a gauge
some require a special adapter
I would have to research yours

but I suggest you first try experimenting with the effect of the primer bulb-
its there already - and could provide very helpful clues

[Grumpy_one]

"safemode" - if Yamaha uses that term (I don't recall)
would refer to rpm reduction for high temperature, or low oil pressure
you would get a warning horn, and an indication on the tach or CL gauge.

Which I don't get any of (warnings that is), and that's what the tech called it, "safemode". But judging by the video, there's a bump right after the initial stall, which to me indicates fuel starvation.

now, that engine also may have a "over-rev in neutral" control -
which would cause rpm reduction somewhere over 4,000 rpm
IF the switch were defective
and YDS would be helpful for seeing that
(btw, if you want the diagnostic software/cable,
you can find it on eBay for ~$60)

Software not compatible on a Mac, (found a cheap laptop on CL for 75.00, should do the trick)

but it seems you are describing a fuel problem
i.e. the HP fuel pump is not supplying the fuel rail at WOT
probably because the VST is running empty

the faster to rpms under load, the greater the fuel demand-
its certainly plausible - for various reasons -
that the VST is kept full at lower rpms
but not at or close to WOT


could easily be the LP pump itself is fine, but hamstrung by something else


some models has a handy Schrader valve on the rail to attach a gauge
some require a special adapter
I would have to research yours

but I suggest you first try experimenting with the effect of the primer bulb-
its there already - and could provide very helpful clues

and lets say the bulb is soft during the event and I manage to fill VST with bulb and manage to continue with WOT, being I have already changed the VST filter, I'm guessing I'll be looking at the filter just outside of the VST pictured...


Thanks Fairdeal

[Donnie Coulsting]

I have the same motor and had the same issue a few years ago. I had to replace the VST filters (inside and out) and it solved the problem. Quick way to check if the VST is getting enough fuel. While running at a higher RPM and the engine stumbles have someone pump the bulb. If the motor starts to gain speed then you know it’s a fuel delivery problem. Did you happen to check the bulb when the engine stumbled? Another issue i had was a clogged intake inside my fuel tank. I thought it was the VST again until i noticed the bulb was deflated. If the bulb is deflated then you limited the restriction between the bulb and tank.