My boat went into the water yesterday and began to leak. It looks like the starboard Y exhaust tube is corroded at the base and is leaking. The boat is new to me but was sitting in water all winter with salt water in the bilge. It needs to be replaced. I assume there is a fitting where it goes thru the hull. Since this will require the engine to be pulled (4.3 L MPI Mercruisers) I want to be sure that everything is done right the first time. I do not want to go through this expense twice. A certified Mercruiser mechanic will do the job but the more knowledge I have the better so I can be certain no short cuts are taken.