I want to thank GARY PENDER, TEAM BROWN STRIPE & GARY PURDY for helping me solve the problem.
Apparently, it was the impeller (had taken a curled set). Except, there might've been a complication in that the top rubber ring that seals the top impeller cavity to the shaft WAS MISSING. I don't know if it got chewed up, OR I failed to install it last year when I replace the impeller.
I elected to try the impeller kit BEFORE taking the poppet valve apart. And, now that the cooling system is working very good, I still want to take the poppet valve apart 'cause it's never been serviced. However, I'm very curious to know exactly why this type of poppet valve was designed into the system in the first place. In the diagram it looks too complicated to be just a simple safety valve. I'm wondering if it's a pressure regulator?
Thanks again

on my johnson I think the poppet is also a bypass, allows the water to bypass the thermostat till it opens I think. just my best guess.

Relieves/regulates pressure at higher rpm. If it ain't broke don't "fix" it. It can be very contary with tha sealing process sometimes. Best not to "service" unless ya got a replacement handy in case something doesn't go just right.....jmo

I agree, If you going to take apart just replace. They are not exspensive and if they don't seal upon re-assembly you'll wish you had not taken it apart. Not hard as already discussed but a pain in the stern.

Yeah! Wake me up!
My laziness, PLUS Murphy's Law, every things points to just buying a new poppet and throwing it in the parts box(in the boat).
Works for me, THANKS