I've never seen an Ottawa,however my Dad had a couple of "buzz saw" types that he ran in the 1950's and '60's.They were built by the Hampton Machine works in Joplin.Pretty much the same overall design.They were powered with cast iron Clintons,rated at about 4 to 5 hp.
If you knew how to use them,you could down a lot of trees in a hurry.
Basically you ran the blade with a lot of "set" to cut a wide kerf.You hit the felling notch side about a third through and took an ax and popped out the notch.Then "clipped" each side a little to loosen it up and then moved to the backside and made your felling cut.Usually no wedging was needed,if wedging was needed a couple of Dogwood "gluts" went into the sides.Generally speaking,the operator used the right side of the blade almost all the time,using the right wheel as the pivot point.I don't remember ever using it with the blade vertical for bucking.Most limbing was done with an ax (limbs over 4" the Mac 1-43 took care of) and used the Mac to cut to about 12' lengths and stacked in piles.We had a 36", 3 point hitch "buzz saw"saw on a 9N Ford to buzz up the "pole piles" into stove wood lengths.(The whole process was much faster and more efficient than using the chainsaws that were common at that time.)
Go buy it and give it a go,they're really neat old tools.I've rambled on enough to give you the idea of how they work in the woods.