I believe you are correct in your feeling that there IS a problem. Those engines have pretty small water passages that can (and do) get clogged with sediment etc.
I would pull the powerhead and check the grommet where the copper tube connects at the top…..and then pull the covers and look at the passages. Plan to spend some time figuring out exactly where the water flows. Some of the passages are hard to see.
If the motor was run in salt-water (as most of mine have) ….then there is even more reason to check these areas out.
Photo courtesy of Paul Moir
See the bend in the water tube? And see the Grommet (#12)
