Mercury part question
 

On my Mercury 2.5L 200. Under the starter in front of the wire harness connector is a fitting with a hose on it. It currently has a bolt in it blocking it off. What is this for? I cant find anything on the exploded diagrams on boats.net . Its the corroded fitting.

http://i272.photobucket.com/albums/j...bracket010.jpg

not sure, but it might be where the hose that send crankcase pressure to the oil tank hooks into the crankcase. if you have the oil injection disabled,someone could have just capped it off with a bolt

What he said. It's a check valve that diverts crnkcase pressure from #6 to pressurize the oil tank to feed the engine mounted oil tank.

if you want to do a better job of it, just un-thread the fitting and replace with a pipe plug