Yamaha 115 four stroke

Anyone know anything about why this engine runs out of fuel while idling around 1000 rpm? Thought fuel pump so put on a new one but issue remains. Tried most all bypasses in fuel system but can’t pinpoint the source. I can idle for 2 to 3 hours in early morning without stalling but when sun rises and air temps heat up it will happen. I have to pump the primer bulb to restart. It’s a 2014 with 4000 hours I purchased new. Any help appreciated.


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

Check the VST filter, specifically the o-ring behind the filter.

That’s where I’d start

Then I’d check the fuel lines and ensure they are not collapsing when they get heated up a bit. They are 6 or 8 years old now with 4000 hours, those are highly suspect as well.

That’s what I’d check next

I bypassed vst filter because I have a water separator before primer bulb also hooked 6 gal tank directly to engine to bypass hoses from boat tank or pickup tube. Mechanics don’t seem to know what it is so trying to find maybe someone that had similar problem.
Thanks


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

Have you tried cleaning the IAC (idle air control valve)?


RBF

Robinette’s Bend Forward

Haven’t heard anything from Chris in a while? He’s good with this stuff. Maybe check your add on Water separator, might be catching air around it?

No. Worth a try though will do. Would the IAC valve sticking cause the VST tank not to refill because I believe that’s what is happening. When it occurs I have to squeeze primer bulb around 30 times to hard.
Thanks


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

Yeah Chris was great he could probably diagnose this. Yeah I bypassed the water separator when I hooked the 6 gal tank to it.


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

Yo Bay…
You state you bypassed the original fuel system with another tank.
Different Bulb???No ethanol???

If no…and you replaced the manual feed pump to the vst…your “mechanic” would measure pre vst and post vst pressure.

As the day heats up should be irrelevant to the motor running…unless the less dense air is altering fuel mixture.

When is the last time the vst tank was drained???Checked for screen blockage???

Since the bulb must be pumped…I would venture it is an air leak prior to the lift pump/vst. Start at easiest repair.

Palmer should be along after he gets done looking at foxes.

Plenty of folks on here that gots engine fixes. Chris…straight answer…after diagnosis…what makes a good mechanic.

Could be the internal vst pressure pump is heating up and delivering less pressure…

You gots to love boats.


The ENTER-NET Fisherman

What are you doing Bay???

As an older electric motor gets old…it isn’t as effective as new. Do i need to post a vst link? It’s not the fuel filter up front.

It’s that big piece of metal behind the intake manifold you gots to takeoff to get to…thus measuring pressure to save work.

It’s planned obsolescence my main. Check for leaks first. New pump about $80…“No price on a good time.”


The ENTER-NET Fisherman

I’m busier than a one armed paper hanger! You may have resolved the issue, if so I will defend your honor the next time someone refers to you as Lloyd Christmas. I put a new bulb on this morning and a squeeze test on the old one wouldn’t hold suction so that may very well be the culprit. Should know soon but I’ve already given Fred a Franklin to deliver to you for services rendered since he was headed in your direction. Hope there’s not an IGA in route or that dead President will feed his pork chop addiction.


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

It weren’t the primer bulb so gonna pull the vst tank and have a look see just when I need it the most ain’t that always the way.


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

Bay, before you pull the vst tank

  1. Turn the key on and listen to the pump…it will activate pressurization.
  2. If it runs out of fuel while running…it isn’t necessarily the pump unless the motor in the pump gets warm and fails.
  3. When you run an engine from another tank…use no racor fuel filters that are in your boat. Seperate fuel line/bulb/tank.
    The racor could have a pin hole…bad gasket…cross thread…you got a leak if it only happens at idle.
  4. Measure fuel pressures going into and out of the vst tank.

What happens if you don’t idle??? Does it run fine from throttle advance to plane???


The ENTER-NET Fisherman

Only during idling all other speeds are fine.

I gots 5k worth of plastic n chips in my ears and still can’t hear from growing up on guns and rock music “Nobody’s fault but mine!”


“ RBF, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

So my shade tree mechanic and mdaddy told me to try a few fixes but nothing fixed the issue. Time allowed the mechanic to pull the vst tank and clean and inspect. What he found was the side cooling chamber was almost completely plugged with salt residue which he cleaned and replaced. This cooling chamber keeps fuel in vst tank at least water temperature so being mostly plugged caused fuel to heat enough to vapor lock fuel pumping but primer bulb had enough pressure to fill vst tank thus the reason for later morning stall after air temperature increase. Ain’t got the bill yet but he said the gaskets were almost impossible to locate and were quite expensive when found. The fix to help avoid this again is to flush the engine with the garden hose attachment below the cowl when I do oil changes.


“ RBF aka Shunkey, Porch Dick, John Weaver, quite frankly you are full of schitt. In my opinion you are primarily to blame for the degradation of this particular fishing website. You dilute this place with your incessant desire to be relevant by posting constantly whatever cut and paste cartoon or quip you dig up only God knows where just to be "heard". It really must be miserable where you are, if not for you then for those around you.” EF 4/27/21

This is what I used when I replaced the pump in my VST tank on my 250 Yamaha and didn’t have any problems.

https://www.amazon.com/Permatex-80019-Aviation-Gasket-Sealant/dp/B000HBM3QQ/ref=asc_df_B000HBM3QQ?tag=bingshoppinga-20&linkCode=df0&hvadid=80401840125115&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4584001418869333&psc=1

Good luck Bay.


The ENTER-NET Fisherman