I've never owned a boat and I know nothing about them other than driving my grandfathers as a kid. I just bought a 71 Mercruiser with the 165hp inline 6. I knew it had a small hole(pic http://duckwebber.net/joomla/images/hole.jpg ) in the lower unit but after I got it home I noticed a 6" crack(pic http://duckwebber.net/joomla/images/crack.jpg ) in it as well. When I removed the drain screw and loosened the vent screw, light brown water came out, then finished with maybe 3 tablespoons of oil. I found a used lower unit, that I'm going to purchase when my wife gives me my next allowance , I'ts from the same boat, with same motor, will I be able to switch them out? Any advice would be greatly appreciated.<br /><br /> http://duckwebber.net/joomla/images/boat.jpg <br /> http://duckwebber.net/joomla/images/boat1.jpg <br /> http://duckwebber.net/joomla/images//boat2.jpg <br /> http://duckwebber.net/joomla/images//boat3.jpg