"RonLong..... The components a
"RonLong..... The components at the top of each cylinder head are enclosed thermostats, coupled with water bypass valves. Both cylinder heads should be operating at the same temperture. You can run the engine on a flushette (hose) and get a general idea of the head tempertures simply by feel. If one is running hotter than the other, or if one is running cold, you can pretty well figure that a problem exists in the thermostat area.
When the thermostat(s) open, water will exit via the slots/holes just above and to the rear of the cavitation plate (the plate just above the propeller).
Pertaining to the water telltale outlet flow, there should be a strong flow out that hose at any speed. There's always a possibility that the water pump is on the verge of failing. Better to remove the lower unit to check the water pump than to find out the hard way.
As Zeke mentioned, you would be well advised to obtain a OMC service manual which may be available at this site. One mistake could be quite expensive! At the left of the page, go to Classified/Outboard, then look for the manuals. Good luck.......
Our questions require answers. If you refuse to answer our questions, how can we answer yours?