I am replacing my lines from the tank to the engine and just got them all removed. I have marine grade 3/16 and 5/16 line to replace it with, but I can't tell where I should use the 3/16 and where I should use the 5/16.
Is the line at the back of the engine the inlet line (3/16)? or is the line that is towards the front (the buried one behind the fuel filter the inlet?

Any help would be appreciated.

(I have searched)

 

suply line goes to filter return line should come off injection pump

 

You can use the 5/16" for supply, but I think stock is closer to 3/8"..., 3/16" for return. Both lines go to the back of the head (assuming you haven't removed the hard lines to and from the supply pump). The supply will have a 45 bend to it, iirc.

These are just illistrations from the 6BT manual, for reference...

Ignore the Vice Grips...it's a supply pressure diagnosis picture...


The hard supply line then goes down to the fuel heater bowl (assuming you still have one)


Then it goes from the supply pump up to the fuel filter and from there to the rear driver side of the injection pump...


The return come from the Overflow Valve (OFV) and goes along the block back to where the Vice Grip picture shows.