2018 Yamaha 40 HP that dies after about 20 minutes

[Laguna 20]

I have a 40 HP Yamaha (F40LA) that seems to run great for about 20 minutes then dies out, if I try to restart it will start then just die. If it sits overnight, it will repeat this same pattern.

I have plenty of Fuel, checked the fuel separator (No Water/and cap is tight) The Fuel filter look a little dirty but couldn't get the bowl off to clean or inspect. The temperature gauge is good and isn't overheating. Also checked the Oil and it's full and clean.

I've had this motor a couple of years and it's always ran perfect.

Does this motor have any sensors that will stop this motor from running for safety reason?
Any help would be appreciated.

Thanks/Jerry

 

[cyclops222]

That pattern can be a electrical part that heats up and fails like clock work. Do a spark plug check on all cylinders. See if no spark is happening on all of them.

 

[99yam40]

No sensors that will kill the motor.
have you tried pumping the primer bulb to see if carbs or VST(if injected) need more fuel?

as soon as it dies turn the key off and drain the VST of carb bowls to see if there is still plenty of fuel in them.
have you tried loosening the cap to see if a vacuum is forming in the tank due to a vent plugged up and not letting the fuel pump move fuel?

 

[racerone]

Check lift pump ?-----Test run with another tank and hose.

 

[Laguna 20]

Things I've tried..
* Squeezing the fuel ball while trying to keep running, made no difference.
*Checked for Spark, good.
*Checked for water in the fuel separator filter, no water and the drain screw is tight.
* I did notice the air screw on the gas tank was closed tight, I loosen it and will try running the motor again this week. However I don't recall tightening it and it ran great before this problem started.
* I ordered a small gas tank which should arrive today as suggested by RaceRone, we'll try this tank the next time it fails.

Appreciate the help guys.

 

[cyclops222]

A vacuumed down gas tank will take hours to leak out a complete vacuum.
Great observation about the screw being closed. Somebody did it. It could have vibrated straight down ? Back it open and put a little pressure on the screw to make sure it does not drift down again.