if that's wat you call majority of smaller boats running river and marsh

I can't answer that, I am not familiar with excel.
D

1995 17ft Louisiana Traveler with 70 HP Evinrude and stainless prop.
Runs 38 to 42 mph depends on if I fish alone or with someone else plus extra gear.
Lost 2 mph from when it was new due to a year ago I had a 2" hair pin crack fixed and slowed it down to 42mph.
When it was new I gps it and it got 44 mph which was very scary and you could only run that in a straight canal with very little or no wind.
Avg speed I run it is 36 mph gps and that fast enough.
Fixing to sell the boat and get a 2012 Weldcraft aluminum boat with 60hp mercury.
http://i42.tinypic.com/2ryt2mv.jpg

That old 70 JohnnyRude was one of the best motors ever built. Check out APBA SST60 Class, watch a few videos on youtube, that is your old 3 cylinder OMC....
D

I had an old '76 50 HP Rude. It was easy to start and very reliable.
Had some reed valve issues with it once. That's it.
But it weighed a ton and had a huge powerhead.