Kawasaki 29hp FI liquid cooled - after 30+minutes...

Question

This is on a Cub Cadet m60 ztr mower. After mowing for at least 30 minutes the engine smothers like it is running out of gas. Fuel filter appears ok and it runs strong for a good while before the first event. After it starts smothering, I let up and let it catch up but iit does it again and the again at shorter intervals.
I had previously used an on line manual but can no longer find it.