Seasick, correct me if I am wrong but the starboard rear is the tell tale (picture shows water). Not doing anything at lower limit yet. Never had high temp sensor alarm go off but to be honest not even sure it functions. Speed is close to gps so thinking it is ok.
Should I have seen water come out of tell tale when I put a hose on the flush connection?
you had the right tube. It certain looks good in the picture.
Yes, it should pee when on the hose. If not there is a high likelyhood of gunk in the Tstat and the pee hole and/or the cooling channels in the head.
Do your gauges indicate temperature or only alarm if overtemp?
You can compare engine temps. Start them at the same time. let them run.. Feel the water coming out of the pee hole. It will get warm when the Tstat opens.
Figure out if the motor is actually not cooling.
I would not waste time though...
I would order two Tstats and two gaskets for the t-stat covers. While waiting for them and a impellor kit to arrive, I would remove the T-stat and look at it for obvious gunk. I'm not going to get into the "boil the Tstat" waste of time. if the Tstat doesn't look brand new, change it. If it looked bad, look at/change the other motor's Tstat.
Start fresh.
There are oddball cases where the impellor is damaged and sometimes/sortof pumps water and sometimes not. A head can be severely gunked up and not have good water flow.
There can be enough gunk at the tstat to prevent the water from flowing to the pee hole.