Re: Water over back of transom
I've owned two Livingstons (12' & 14') and have had to do transom lifts on both of them of about 1.5" to 3". First, I think the factory spec freeboard on the transom is too low (particularily on the 12') which runs you the risk of potentially getting stern swamped. Second, long shaft motors tend to sit too low in the water on Livingstons in general which results in decreased speed and efficiency. From my experience, you want your outboard mounted so that your outboard fins align exactly with the very base of the center-line mini hull.
There are two ways to do a transom lift:
1. You can go to a metal shop and have them fabricate a u-shaped piece of galvanized steal or aluminum that fits snugly over your rear transom. You can then cut a piece of redwood or a CCA treated 2X4 to use as a spacer/lifter. You'll also need to run some heavy duty stainless bolts through the metal and transom to secure the metal transom lift in place. Make sure you use washers and silicone to seal water/rot from entering your transom through the drill holes. Try to place the drill holes above the water line as much as possible as well.
2. An easier and cheaper fix is to cut two 3/8"s pieces of aluminum and bolt them together through the fore and aft sides of your transom. Again, you will want to cut a piece of redwood or a CCA treated 2X4 to use as a spacer/lifter between the two mounted pieces of aluminum. You can also hopefully buy a cap piece of aluminum from a marine supply store that you can screw into the 2X4 to hold it in place.
One more thing. I also install a drain and plug in the back of center line hull. If you don't, water from the deck will eventually find a way seep in and add a lot of additional weight to your boat.