In all HONESTY If someone is looking for a engine, I would have to say GET A ZENOAH. Most other weeder engines need moded to make some good HP and the mounting and stuff.
Zens can take the abuse in a boat, dunks, hydros, and then as you want more and more speed you can mod out the zen and you have a whole new animal on your hands.
I did the "cheeper" enignes, and it ended up costing me that cheep engine and a zen in the long run.
Now i did build up a SIKK 27 this winter from a zen 23 lower. Its a 2 bolt head, it has a crap load of torque it seems, "bench running only"
But the 2 bolt cylinder has me worried about dunks.
there price is about 50 less than a zen, but its not a zen.