I am with the previous poster- replace the line.
But you also need to find what caused the pinhole. Pinholes in steel
lines just don't happen without a cause. Is the line severely corroded due to saltwater? In some boats the vented loop leaks
and if it is mounted over the engine
will spray the engine with saltwater. The solution is to clean the loop valve and install a small section of hose and route
to the bilge
This happened on my J/32.