Thanks guys for the advice
The main issue is that this boat was a birthday present from my brother and therefore holds strong sentimental value to the point that I don't want to "replace" it and have this sitting around
As the second point, I have no idea how often I'll be using a boat either. I am moving countries soon, and where I am going the closest water would be the beach
Thirdly though, I have "solved" the power issue by planning on running a 15CVRX (with marine heads on it) and then using a larger engine in my car, which I also wanted to do but could never justify it as the 15 in it now is very new and performs well. Just when I bought the OS engine, I didn't realise 18 would fit as well.
So, in reality I am left with 1 problem, that being what I stated above that the U joint wears out quickly.
The other posts asking about struts and rudders, was just trying to gather information about doing a whole rear end swap so the prop is stable and doesn't move.
Of course again, depending on how much use the boat gets, it might still be cheaper and more worth my time to just keep replacing that U joint. I have a spare one still, so I am assuming I should have a good few 10 or so hours before it really is time to do something about it. I guess by 10 hours though, I should have a better idea of how much I'll be using the boat
So this is why, I am trying to find a cheap and easy alternative to all this