I'm more concerned about my home, I know the boat is dry but our homes down here are not set up for this coming artic blast. the heat pump is practically worthless but I have firewood.. I suspect that the plumbers will be busy next week...
Maybe you could rig up some cable steering, I built a small hydroplane and wire rope worked well. The throttle was easy but it didn't have a gear shift.
If you have the room to work on it then lifting from the gunwale will work. Your tree would work as well. If you have doubts then brace it but in both cases I think you will need to stablize the hanging engine or you will be chasing your tail when wrenching...
I didn't ride during the covid reign of terror but got out a bit this summer but father time has a way of putting a pause on long rides so I stay close to home these days..
What engine is it and is it running now? If it has sat for a while then your measurements are not useful. It will run with the numbers you have given but not well but I think if you get it started and running the numbers will be more accurate.
Best I remember the tube that the cable fastens to has two flat areas on it that you put a wrench on to hold the tube in place when tightening the steering cable. You probably need to find a manual and it will explain it...
