Mercury fuel issues after motor off for a while

[TheHillKid]

I have a 2005 Mercury 150 outboard carb. model and I continue to have issues when the engine sits off for a while. When I go to crank it after sitting it will crank then die if I do not choke it. Sometimes I have to re-prime the bulb.
I have done the following to try and resolve the issue and still not resolved.
- replaced the one valve on the gas tank.
- replaced the fuel lines with marine fuel lines to the motor. I have not replaced the ones on the carbs.
- replace fuel pump.
- added a one way valve in the fuel line before the fuel pump just to see if I was loosing prime.

 

[Texasmark]

I guess the next thing to do is to do carb kits and check the float setting. Your needle valve in one or more of your carbs may be leaking or the float is not sealing the needles properly. Assume the engine is sitting vertical the whole time you are stopped, or close to it. If tilted up during that time, pull your sound box cover and look for fuel puddling in it. That would be a sure-nuf give-away that your needles aren't seating.

 

[ondarvr]

First, priming the bulb and and using the choke are not unusual if a carbed motor has been shut off for a while, if that's all that's needed for it to start then you found your solution.

There are some conditions that can cause this, if you search "heat soak" you may find some old threads about it.