paul,

i was looking at a picture of an air-cooled omc rotary
on ebay and started thinking. it has a direct-drive
cooling fan, i've also seen a picture of the curtiss
wright air-cooled rotary which has a geared fan which
looks like a turbine engine. do you have any idea how
much horsepower theese would consume versus the water
pump on a water cooled engine?

gary
midland tx

No but a lot. Porsche built a fan cooled engine for
aircraft and it had a worse BSFC than a Lyc or Cont.
On the other hand a there may be less aero drag.