In a message dated 9/19/2004 10:26:54 AM Central Daylight Time, billdube@killacycle.com writes:

<<  As I understand it, the exhaust porting on the Renesis is completely different than the 13B. The exhaust runs much cooler in the Renesis because of this, so I'm told. It is likely that a significant fraction of the heat that is not going into the exhaust is going into the water jacket instead.
 >>

The new engine has double the area exposed to the exhaust flow, and that in turn is exposed to water cooling. In the Periphery exhaust port, the same thing happens because the exhaust flow is through aluminum and that transfers heat really well.
To save money on additional cooling, they install a stainless sleeve in the port to insulate the aluminum from the exhaust flow. The new engine has only the advantage of a cast iron port and it does not transfer heat as well. So the water temps will be higher by some amount. I doubt that it would be by a spectacular amount, however.

Stainless liners for at least part of the port might work well.

Lynn E. Hanover