Surface temps were 37.4° - 37.8° where we fished Sat/Sun. We fish a deep (330'), clear, reservoir in NE WA that, in my biased opinion, has the best "silver colored bass" (aka rainbow trout) fishing in the state.
Wanted to share how I keep my Optimax happy and how a Smartcraft instrument can save your backside with useful information you won't get any other way.
My personal practice in cold water, which is almost every time I launch including summer (~70° surface temp) is to not accelerate until reaches thermostat temp. To do this, I bump throttle to about 800rpm, observe coolant temp on Mercmonitor watch it climb, stats open, temp drops, then as temp begins to climb again, gradually accelerate to cruise rpm, which may take 3 - 4mi. I will sometimes repeat the thermostat cycle twice for my personal comfort.
I have experienced an iced poppet one other time and it happened again Saturday after we launched, and without a Smartcraft instrument, there is no way to know.
Water pressure 1.6psi. You and I discussed a similar situation, under almost identical conditions, maybe 4 or 5yrs ago, determination was a frozen poppet. Same conditions this time, couple weeks of really cold temps followed by a break and boat stored in unheated metal building.
Since coolant temps were cycling normally from idle to 800 - 900rpm, and climbed only when attempting to accelerate, I knew the poppet was frozen.