When you have the Water Jacket Cover off, check it for Warpage. If it is, a new Gasket will also leak in short order.
In regards to the Power Trim... Here is a pic showing the 35hp(rerated 40 back in 84) and the 50hp. The 50 uses a different Yoke and Transom Brackets that do have provision for...
Most Weed doesn't smell like Skunk. It has been so long since I smelt any Skunk Weed, I forgot that it existed
However that said, A Skunk still smells better than a Smoker. Smokers Reek
I wish the Stench Sticks were $500+ a Carton. And Ban Smoking of Tobacco Outdoors, and in Houses/Vehicles with open Windows.
Pot and Hash are okay, as they don't Stink anywhere near as Bad as Tobacco
When you changed impeller, any chance the Drivepin/Key for it didn't get put back in?
Also any chance the Water Tubes didn't go in the Grommets at the Water Pump?
Some Basic Troubleshooting for open/corroded Circuits. Have you verified that the Horn works, when supplied power directly from the Battery, using 2 wires?