Well Rexone I think we are going to have to agree to disagree on this one. I do appreciate your lengthy reply, and I'm sure you have not had issues with your T-stat units. I wasn't implying that you would sell a bad part, I was merely saying I don't think it is a desireable application on a raw water cooled motor. The ONLY way to get water to get hotter when your are starting with the same 80º water from the lake, is to keep it in the motor longer. That means lower gph flow rate. There is no way around that. You have the same motor operating at the same workload, pulling in the same water from the lake your gph flow has to be lower to get a hotter water temp.
My temp sensor reads 145º cruising. My oil temp hangs around 235º-240º. Under stress or harsh conditions it will see 250º+ oil temp. I ran a closed system in the same boat, same motor, identical oil temps, water temp was reading around 200º with and Evans coolant system.
I've done a fair amount of research on flash boiling around the combustion chamber. I'm not saying that you will have boiling problems with a t-stat regulated system. What I am saying is that the water jacket around the combustion chamber gets much hotter than 212º F. This causes tiny steam pockets to form in these "hot spots". These steam pockets tend to insulate these areas and retard the heat exchange process. I'm not saying that your water will boil out of your motor.
There is NO correlation between a closed system car engine that won't get over 140º at cruising speeds and a raw water boat system with the same temp reading.
True, water will not boil at 180º. BUT it does mean that since your gph flow rate is down in a t-stat regulated raw water cooled marine engine that is higher water temp combined with a lower flow rate, lends itself to more flash steaming around the hottest part of the heads, the combustion chamber. I've worked on motors that were detonating (some badly, some mildly) and were only showing water temps in the 190º range. Combustion chamber temperatures have very little to do with water temperature. Since we can't run an anti-boil coolant in raw water systems, the best defense is pressure and flow rate to limit the tiny steam pockets.
The testing with the Evans coolant showed that they could run coolant temps of 220º+ with no detonation. Since the Evans coolant was so resistant to boiling, it was able to pull more heat away from the combustion chamber. Now Evans is a real pain in the ass, because it's expensive as hell and you can't add any water to the system, but they do show that water temp does not necessarially correlate with detonation.
It all goes back to the fact that you can't heat water up over 100º from ambient without reducing it's flow (restriction).
Getting weeks or debris in the inlet hose is much less likely because if something lodges in there (prior to a bypass valve) the pressure would skyrocket and hopefully blow out the restriction. If you get a weeded or dorked up T-stat, the bypass valve would limit the pressure to 15 psi or so, which could drop the water flow to the motor to nill.
Nick