Re: dropping the lower unit?
i just did this today.
There is a screw that holds the shifting shaft in place. I think its either 7/16ths or something, but it has a slot in it for a flat head screw driver. Once you get that out, move down.
You take out the four bolts you took out ( 9/16ths ) , and then proceede to the trim tab. Take out the bolt that holds that on, again its either 1/2 or 7/16ths and take off the trim tab. Under it, will be another bolt. Now, on the two 115s i have, it was either 3/4ths or 9/16ths, depending on which one i was working on. I think there might be another bolt as well, there should be a 5/8ths somewhere as well.
After that, your going to want to pull straight out, do not wiggle or push the lower unit side to side too hard, as you don't want to damage the spline. It might be hard at first because they might be stuck together a little bit, but otherwise after the bolts are out its straight forward.
Do you know how to do the waterpump?
