2018 mercury opti pro xs looses fuel prime

[toolman2.5]

2018 150 pro xs wont keep fuel primed when at idle . it dies and i have to pump up the ball to get it started again . i have replaced the ball and checked the fuel lines for leaks to no avail. what next to check. the ball isnt sucking flat it is just soft.








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[XstreamVking]

There are plastic fittings on the pulse pump where the fuel line hooks up, could be cracked? Just replaced one that had a hairline crack. Have someone squeeze the primer while you look for leaks. If no leaks found, the leak is before the bulb maybe at the fuel pickup in the tank. You are getting air in the line somewhere, or the pulse pump is bad.

[25two.stroke]

Your original post doesn't say you checked or replaced the lift pump (square pulse pump). This would be my first suspect if no leaks can be seen in the fuel system. If the primer bulb succeeds in priming the system after it looses prime then it is likely (but not 100%) that the tank/pickup is OK.

When you say its loosing prime at idle...is it dying/running out of gas or the bulb is always soft? Because they are meant to be soft when running...they don't stay as hard as when you prime them. If it is running out of gas at idle does it only do so at idle, or does it run our of gas regardless of rpm/load? Those lift pumps have check valves that can chip and/or get clogged, and a rubber diaphragm that can get cracked or worn out and then it won't fill the vst with fuel. sometimes once a motor is revved the siphon effect and high pressure pump can keep it going and mask the symptoms of a failing lift pump. Thats my 0.02 ... in addition to those items mentioned above

Read this about primer bulbs https://www.screamandfly.com/showthr...x-squeeze-blub for SS Minow's reason I try to never install them unless the system absolutely needs it.

[toolman2.5]

it runs out of fuel only at long idles . as long as you are running above 2000 rpm it is fine. at idle it doesnt pull fuel and the line and ball go empty.

[DangerNewb]

I'm going to jump in here with a similar problem. 300xs with 20 hrs on it will fairly often stall when I throttle it to get on plane. The bulb will be soft. It will stay idling indefinitely. But quit when I throttle it.

Randy with liberator told me he found the xs motors to be bad about this and started installing fuel pumps in the boat. I have 2 engines. Only 1 does it. Haven't gone the fuel pump route but its aggravating. Seems it does it after a long idle. If it doesn't idle long it seems to not happen.