1985 V4 Evinrude 90hp VRO - vapor lock?

I had the above engine worked on. The VRO pump was bad, so they took it off and I mix the gas now. The engine was worked on last winter. I fired it up after a little tuning this spring. It ran great, no issues EXCEPT - once the motor is off for a day or so, I can not get the plunger to prime the gas lines. The plunger is new, so that can't be it. The mechanic put a small metal box that connects the gas lines and I take what used to be the original CRO oil line. If I remove that box and press the plunger, I get gas in the lines easily. I then placed the box back in line and press the plunger again - engine fires right up. If it sits though, I can't get the gas back in the lines until I repeat the above steps. Any idea as to what would cause this?

I can't picture your plunger device. If the VRO is gone, the oil line should be gone too. Usually a primer bulb that you squeeze should be installed in the fuel line. If the bulb won't fill with gas, the usual cause is an air leak or excessive restriction between it and the tank. The valves in the bulb could be failing as well.