I would put that limit, with wet cylinders at around 65-70 minimum. 50 is scary low.
That engine is hard to kill.
Worked on one today as a matter of fact. After putting a water pump in the same engine a couple weeks ago the engine came back for a repeat shutting down issue. While working on that I did a digital temp reading on the cylinder head and block. Block was at 132f and cylinder head was at 230f. Just a tad warm. The engine didn't seem to care! There are a bunch of other engines out there that would have stuck by that time. Pulled the cylinder head and found water jackets packed with sand and silt. Removed the gunk and it ran 108f and around 150f. Good to go. Shut down issue was a filter with too fine a screen in it that would not flow fuel when the tank got low.
Anyway.....when you get the engine going run a ton of engine tuner through it. These little guys really respond to it and clean up well.
The little 3hp engines are ones that I plan on always having one or two around in my arsenal for fun. They are that good!