If it separates after tapping, you have cracked it in two, since it is one piece. The thermostat is secured in the water distribution
manifold with a retaining ring. The thermostat sits up against a ledge or counterbore. The retaining ring then goes in a groove in the
manifold to keep it from dropping down. To remove, turn the manifold upside down and pry the ring out. You will the be able to remove the
thermostat. If you need a diagram, look at page 5-11 of the OMC Cobra manual.

Jim wrote:

"Lawrence James" wrote in message thlink.net...
If it's anything like a merc the housing is two pieces.

That's what I first thought too, but this looks like it's all one
casting. Maybe I need to tap it little to see if it seperates, but it
sure doesn't look like it.