No peehole on this engine, just two small holes on the leg which emit mainly exhaust rather than watter. Reason? Most water travels down the leg as the two holes are there only to indicate mistily that water is circulating.
I made a custom flusher as there is no flushing muff available for this model. Leave motor running until it reaches normal temperature. Hot water eventually comes out.
At the end of the video, see how to test that the impeller is pushing the water up the inlet pipe (borrowed from an excellent youTube video).