A high hp/liter engine will likely require 2 keel coolers. A John Deere 6081 (8.1 liter) 375hp only requires one keel cooler. I spoke with the Deere dealer a few days ago and they mentioned they were going to keel cool the new 500hp 9 liter which would require 2 coolers. The customer wanted 500hp, but also needed the engine keel cooled. For comparision, the 425hp version of the Deere 9 liter requires only 1 cooler. I believe for most modern engines, a company like Fernstrum can tell you what cooler will meet the requirements of a particular engine.
A friend of mine needed 2 coolers for his 500hp C9 Cat. Another friend needed 2 coolers for a 370hp 5.9 liter Iveco. I believe you can keel cool any engine so long as you have enough cooling capacity.
I'm not up to speed on keel cooling big engines. But in my "mind's eye" the benefits would be @ the least.......
Benefits of keel cooling:
Non corrosive 50/50 antifreeze throughout the WHOLE cooling system.
No raw water pump with an impeller to worry about.
No worries about salt water intrusion backing in through the exhaust.
No worries about the engine "burning" salt water through a leaking aftercooler.
No "winterizing" the SWAC system.
Drawbacks, if at all:
A dry exhaust.
A knot or two of spped loss?