coolant

"Waterless coolant is not permitted for engine types 916 iSc B, 915 i Series, 912 i Series or for 912/914 Series with cylinder head version Suffix - 01."

Anyway, "conventional coolant mixed with water has the advantage of a higher specific thermal capacity than waterless coolant."

Hi Wayne

The main issue for the engines the new head design, changed when they started the injected series, is that they have smaller coolant volume in them.  this allows for the fluid to move faster in the jackets around the head for improved head cooling.  This is a problem for Evans however in that it is more viscous and for that reason any of the new Rotax versions with the newer castings should not use the waterless coolant.  The small volume heads are all found in the 912iS series and 915iS series.  All of the carb versions with the suffix added to the serial also have the small volume heads.  In general pusher aircraft have more heating due to the fact that airflow over the engine is not as focused as it is with a tractor application.  It may be that your solution might be a larger cooler or as many OEM are doing with the injected versions an electric fan like your car.  The injected run hotter anyway, especially on ground running, due to the dry intake manifolds (it is a multi port where the fuel is introduced just before the valve)  With a dry intake and runners you get no cooling effect from the fuel in the intake as you do with a carb version.  

Cheers