I don't know.....here is the link I referenced to

http://www.cumminsonan.com/www/html/Common/pdf/specsheets/a-1492.pdf

This shows ....yes liquid cooled .....GM engine w/ operating speed of 1800rpm.

Could the 2 pole your refering to (in your link) be the circuit breaker, indicating a 1 phase 240v system??

Or onan has their spec sheets mixed up..............or I'm mixed up.........could be either

Freezing Rain here, I might get to try out my ebay special,

Have a good day,

John