On Orion, we switched to a Nissan 9.8 long remote electric with HT prop last year. Works very well. Would have preferred a 15, but that would have required a shoehorn to install, and would have been a real bear to take in and out, being more than 25 pounds heavier.
Being in freshwater Lake Ontario, the growth is a lot less than you get. We are using Aurora antifouling wax (made in Canada) on the LU and prop for the first time this year. So far, it seems to be doing OK. Be careful using AF paints
on the LU, since "regular" copper bottom paints
will attack the aluminum housing. We never had really good results using any (even TriLux, made for outdrives) AF paint
on the old 'rude OB -- had problems keeping the paint
adhered to the LU.
Our hull (#53) was originally equipped with a short shaft OB, which could tilt inside the lazarette. If we were in a really high fouling area, or racing every week, we might well go back to short shaft to get the LU out of the water during the off days when we don't sail, or when racing.
I was thinking that if we wanted to be able to tilt a long OB, we would redesign the inner "false transom" motor mount, making it an articulated setup. That would be a big job. Since we have a relatively short season (late April - early October) in cool freshwater -- with minimal fouling (except for the damned zebra mussels), it's a lot easier to keep it as is.
I suppose you could open up the outer transom, but you would definitely want to reinforce the cutout area a lot. If you don't motor in huge waves much, maybe a better setup would be to run a short shaft OB, and just tilt it into the lazarette when done for the day.