The the Carb versions are basic in computer control. The large Carb'ed engines meet EPA 2006 and CARB 2008. The smaller engines do not meet CARB 2008. Which is why new model are coming out. The use of Steel cylinders cast into the aluminum blocks reduces weight.
Oil is forced through the engine at high pressure.
Aluminum requires less hp. Honda does not package with boat companies. But we do pre-rigg with a number of boat companies. Price is best left at the dealer level. I'm not up on retail that much.