In article ,
"Roger Long" wrote:

Unless there is a problem with the cooling system, the one hour
limitation (or more typical 10% of operating hours) is a bit of a
figment. The engine will not overheat or be damaged at the higher RPM
and you could actually run at the full "intermittent" RPM all day
long.

Minor points:

I found that at 3400, our Yanmar overheats in just under an hour as
advertised. At 3200, I can run until the fuel runs out. We are propped
for 3400 max, so I'm happy.