Yes you do need to winterize the closed coolant systems. The exchanger and risers need to be drained along with the water system. The coolant stays in the block so it won't need to be drained as in an open coolant system. Definitely more work than an out board.
Not to sure what is included with the Yamaha package,but my evinrude I command is a very nice system. You have a lot of sensors that can be added to the system. Not to mention, the gauges are so easy to see at all times. But I also would not be without the power steering. Remember,build your 1st...
Absolutely love our snap in carpet. I pull it out and Rug Doctor it a couple of times a season and at the end of the season before putting it away in the garage for winter. As for the rest of the vinyl floor,just power wash off the dirt. Still looks great after seven years!
Looks like a great build! The only thing that I would change is the rub rail. I really believe the stainless rub rail is the way to go! And by the way,power steering is a real must! Wouldn't have another boat without it.