Well My baja has twin big blocks and there is nothing like the "oh my god get me home motor"
but think of it this way
2 engines working 1/2 as hard as one working 100%
Now 2 working 100% will give you the torque numbers that a worked single will give no doubt.
but you have twice the prop in the water, more control at the docks with twins.
Also I might get flack for this but small blocks can be built up just like big blocks can, granted no small block is going to push 1000 HP or anything but you can tweak small blocks to push 350-500 HP each but the torque (which is really what makes a boat move) wont be as much as a big block ever. That is why choice of big blocks far and exceed small blocks as a choice in the marine community.
In that size of a boat around 28 SS sonic, twin small blocks move that boat pretty well. It will never be a 100+ MPH boat but really, how fast in a 28 do you really want to go?
That is what it boils down to, how fast do you really want to go?
Also sonic used to put twin big blocks in the 28 for a few years but I think they stopped a year or two ago doing that.
You have to jump to 31 SS now to get twin big's
If your a lake boater and want to be a big fish go for the twins, lower cost of ownership = small blocks by far. Hell you can go to pep boys or any local place and find numerous choices in perf parts for small blocks cheap and new.
I know alot of guys running single big blocks and they dont really complain about it.
All in what you really want to do.
But more attention goes into big blocks these days.
you dont see 10 different choices of outdrives for small blocks like you do big blocks
I understand your dilema but if it were me, having the get me home motor is definately worth something