2013 Yamaha F150xa stalling

[Tigerfan79]

I just purchased the boat (Bennington pontoon) and did the following maintenance:
-new water separater
-new fuel filter
-changed oil
-changed gear oil
-drained fuel from fuel tank and filled up with non ethanol fuel (existing gas was a darker yellow, prior owner said he always used sea foam so I’m not sure if that caused the color change or if it was just old)

This is the problem I’m having, initially it starts up great and idles fine. After idling about 5-10 minutes I went to around 3500 rpm and it ran there about 20 seconds before cutting out and eventually stalling. It cranked z back up but would only stay around 1000rpm for almost a minute then die. Each time it would die quicker until it wouldn’t start at all. Let it sit about 10 minutes and it fired right back up but would only idle for a small time. I can squeeze the primer bulb continuously and that helps but not enough to keep it running. The boat can sit overnight or an extended period of time (hours) then the process starts over with it running a longer time the first time then getting worse each time after starting until finally not cranking.

Things I’ve tried so far are a new primer bulb, verified fuel tank vent is clear, verified when it dies the fuel filter is full of fuel, drained the vst tank and refilled. It seems the fuel issue is behind the paper element as everything forward of that to the actual fuel tank seems oaky. My next though is would this sound like the vst filter? The engine only has 32 hours so obviously it sat a lot since 2013 and was last used a year before purchase but had yearly service by local dealer.

Im open to advice and thank you for your time.

Matt

[fairdeal]

Puzzling symptoms.

In theory, its very simple.
The engine runs off that 'little gas tank' - the VST

If the VST runs empty, then the engine is 'out of gas'.

The VST doesn't, can't, fill itself.

The low pressure pumps should keep the VST full -
but they only work when the engine camshaft is turning.

So once the VST runs empty,
'letting it sit overnight' doesn't fill the VST back up.

Now the primer bulb can / should, be able to fill the VST completely -
to the point where one can no longer squeeze the bulb.

And if nothing else is wrong with the engine,
and the bulb keeps the VST full,
then the engine should run fine, until one tires of squeezing.

[Tigerfan79]

I agree, it has me stumped. Squeezing the primer bulb will keep it going for a short time but then it stalls out. When it stalled, we were able to drain fuel from the vst tank so that is why I was thinking maybe a clogged vst filter not allowing the fuel to flow enough? I had attributed the sitting for a while/overnight to the fuel seeping through the filter and running longer, but I’m not sure if that is how the system works once the fuel is inside the vst tank. Of course, I’m not sure how much fuel we drained from the vst tank or how much should be in there but there was at least 6 oz that came out right after stalling.

[99yam40]

monitoring fuel pressures to and from VST while the problem occurs will tell if the pumps are keeping the pressures in spec

[fairdeal]

I expect the VST holds 8-9 ounces max,
if you drained >6 oz that was enough to start and idle for several minutes.

Yes, there is a screen ('filter') on the inlet of the high pressure pump inside the VST
and that can get clogged enough to starve the injectors of fuel -
although usually, that problem shows up at high rpms, under load;
I can't recall hearing of it preventing the engine from starting or idling.

As 99yam 40 points out,
a pressure gauge will tell you exactly what is happening to the fuel rail
there is a handy Schrader ('tire') valve in the center of the rail for that purpose.

At key on, the pump should run for a few seconds and create ~44 psi.
With the engine running at idle, pressure should drop a bit into 30-something
And then running with throttle open, should be steady at ~44.

[Tigerfan79]

Thank you for the responses so far, I will check pressure and see what it reads...

[TownsendsFJR1300]

Just for S&G's, hook up an auxiliary fuel tank and run known, FRESH FUEL in the engine.

Seafoam works good but as a stabilizer, I wouldn't trust it for any length of time with old fuel..


You can drain a little bit of fuel in a clean container and inspect. Bad fuel will have a different look and smell. Seafoam, being clear, won't change the color of the fuel. Bad fuel WILL..

[Tigerfan79]

Just for S&G's, hook up an auxiliary fuel tank and run known, FRESH FUEL in the engine.

Seafoam works good but as a stabilizer, I wouldn't trust it for any length of time with old fuel..


You can drain a little bit of fuel in a clean container and inspect. Bad fuel will have a different look and smell. Seafoam, being clear, won't change the color of the fuel. Bad fuel WILL..

The gas I drained out of the main tank was definitely a dark yellow color but didn’t smell too bad. I filled it back up with fresh fuel but maybe I do need to pull from a fresh source....

[Tigerfan79]

So today I went through the entire system checking for leaks. Even took apart both low pressure fuel pumps to verify nothing was wrong. Took the vst out and it was obvious the filter was clogged, so bad in fact that you could pour fuel in it and would not drain out at all. I think we have found the issue, now just waiting in new parts to arrive and put everything back together and go run it. The high pressure pump did have some corrosion on the outside but you can hear it turn on so I’m guessing it is fine? I really would rather not have to spend the money on a new one if there are any tests I can run. Thanks again for the advice...

[TownsendsFJR1300]

Great news!

I wouldn't replace the pump unless you know it's bad, especially if you hear it run and it's definitly clogged (hopefully caught all the crap in there and junk didn't make it to the injectors).

I know you addressed water in the tank, might want to re-circulate, try to remove if any more water in there while your waiting for parts.

[Tigerfan79]

I took some steel wool and brushed off the light coating of rust on the pump. Is there anything I can coat it with or will it be fine as long as no more ethanol fuel is ran through it?

[fairdeal]

I don't think any kind of 'paint' would hold up to constant immersion in gasoline.
If you are going to be running E-0, there shouldn't be any water anyway.