Outdrive oil line
 

Which drive do you have? There are replacement lines from Mercruiser or sometimes you can make something yourself.

Its a bit difficult but can be done. In most cases the factory didn't keep the fitting from turning when tightening the nut, so the end is real close to the housing. After removing the old one, take a tie wrap and loosely install over the fitting end. Soap up the hose and use some needle nose pliers to push it on, being careful not to damage the hose. They tighten the tie wrap

What alldodge said, + what year is your drive the older Bravo drives the upper fitting where the line attaches was brass and this is way easier to work with, the newer Bravo oil fittings are plastic and very very easy to break off, if yours is plastic you need to slice the old hose off very gently and lube end of new hose good and slide it on with the zip tie as Alldodge has said. the other end hooking to the helmet area is still brass