Mistery fuel line

[smoothforce]

Need a little help here, I just put back together a 1980 (ish) merc 70 HP triple and I can't find a connection to one of the 4 fuel lines originating from the fuel pump. One intake line comes from the connector to the fuel tank, goes to the pump, from which another line goes out to the fuel filter, then to the carbs. A third line goes to the exhaust plate, provides the pulse that moves the diaphragm inside the fuel pump. A 4th "mistery" line was just hanging by the plate, no connection that I could see when I was tearing the motor apart to replace a piston and rings. Could that be a vent line? There is no place where to connect it. The diagram in several places says to it connects to the exhaust plate, but the plate only has one connector in use by the third line. Your input is appreciated.

 

[Faztbullet]

Thats a water cooled fuel pump...came from factory that way to help prevent vapor lock. The 3rd line is water from exhaust plate, not pulse. Top fitting is water out to "p" indicator.

 

[smoothforce]

Thats a water cooled fuel pump...came from factory that way to help prevent vapor lock. The 3rd line is water from exhaust plate, not pulse. Top fitting is water out to "p" indicator.

Thanks bullet, that is interesting. So I should connect the mystery fitting to the pisser on the back of the motor? I have another fitting coming out of the rear plate, by the middle cylinder, looks like connects to the water jacket (is that what you refer to as Top fitting?) I thought that was the pisser, so I connected that blue hose to a long range pisser I fashioned. I'm still out of idea as to how these 2 connections work and where do I get the water for the pisser. Pardon my ignorance, just need help on this. I have attached a pic of the connector and blue hose on the rear plate.

 

[smoothforce]

Thanks bullet, that is interesting. So I should connect the mystery fitting to the pisser on the back of the motor? I have another fitting coming out of the rear plate, by the middle cylinder, looks like connects to the water jacket (is that what you refer to as Top fitting?) I thought that was the pisser, so I connected that blue hose to a long range pisser I fashioned. I'm still out of idea as to how these 2 connections work and where do I get the water for the pisser. Pardon my ignorance, just need help on this. I have attached a pic of the connector and blue hose on the rear plate. View attachment 391929

Perhaps you are trying to tell me that the pump has an inlet connected to the exhaust plate and one outlet that goes to the pisser. If that is the case, the other outlet on the back plate should be plugged, correct?