What is the difference between a three line and a two line fuel pump on a 79 johnson 85 hp?

[Tony John]

I have a 1979. 85 hp outboard that has a bad fuel pump, I ordered a new one and it is different configuration . The old one has 2 lines and the replacement has 3 what is the third line?

 

[SaltyScot]

The 2 line pump has a hole in the back to receive the pulse which drives it directly from the crank case. The 3 line uses the third line to receive the pulse.

 

[Tony John]

thanks