I just spoke with the Rd Guy at Cenpeco Racing oil, Told him my application and what my oil temp was getting up to, 230-235 when running wide open, He told me that he would not be worried at all, He said heat will hurt the life span of the oil but not so fast that i have anything to worry about. He told me he has many customers that run cars and dragsters up around 300 degree oil temps, dirt cars at 50+ plus laps at 290 -300 degree oil temps and the oil holds up. Mild thunder are you running a blower or pro charger any kind of forced air. Usually these applications cause alot more heat than naturally aspirated engine.

I had my self worried a few weeks back... My gauges both started reading 320 degrees so I was getting concerned.. The second I slowed back down the temps dropped.. I decided to hit it with a gun at the filter (also where the sending unit is). When I hit it with a gun, I was reading 260 on the gauge and 220 on the gun... Gauges are way off... That being said, I'd be running about 280 while running hard.

That's exactly what I found when I hit my oil temp sensor mount with a non contact gun .

Oh so you aren't getting enough water psi. That's strange. You sure the line isn't plugged up with sand/debris ? I have my water pressure line coming off my bellhousing cooler drain

Your statement that "most" oils are designed to operate at 200 degrees is false, the operating viscosity is spec'd @ 100 degrees Celsius (212 Fahrenheit). That's a fact. I think a major oil companies tribologysts knows a little bit more than mercury marine. And mercury uses 210 degrees set point on the modern oil thermostats, so I'm really not sure what your point is? I never said they are wrong. My thermostat is set 5 degrees higher. 220 degrees even in a conventional oils isn't an issue whatsoever. They put these cushions in to protect their interest for the sake of warranty.

Cooler oil is most definitely NOT better in many circumstances. I'm not saying a thermostat is mandatory, however if you are running a 140 thermostat in your engine (naturally aspirated) and no thermostat with a large oil cooler, your oil temps will more than likely be too cold. The oil is not going to be at the temperature for optimal operation. Let alone to burn off the water introduced by the product of combustion.

Ok so 212 not 200 is the spec. I was generalizing meaning that 300 degrees is no where near where oils are tested and rated.

I can tell you first hand for years I ran a pair of blown big blocks in my boat with no oil stats or water stats. Rarely ever got any oil temp. While I have since added a oil thermostat, prior to that the engines were tore down after at least 6 seasons on then running very hard, and there was almost no wear on anything. I never had chocolate milk under my valve covers. The bearings could have been reused they looked so good.

I know you are an oil expert , and that's fine. I try to stick with what works. I think if you go find a merc 1075, 1350, eddie young engines, sterlings, chief, teague, or any of the big builders, you won't find them setting up their engines to run 230+ oil temps. I can care less what redline, amsoil, or any of the oil companies claims that their product can withstand. I care about what the total package can withstand.

I agree with you that 220-230 really isn't a big problem. I was speaking towards the group that feels 275, 300 is just fine because they run a boutique oil. But hey, if they pull their engines down after a few hundred hours and all looks good, than I guess it works.

As for the oil tribalist that works for the big oil company, sure he may know a thing or two about oil. However, mercury knows a thing or two about marine engines and what works in them. How many tens of thousands of mercury engines are out there running great, compared to how many engines the oil specialist has built and ran "his way".

I'm no expert, however I have spent quite a few years studying oil and happen to have a few friends in the biz. I agree running 275-300 is too high in a marine endurance engine. However it is telling that mercury marine(the design hardin is using as well) now uses the higher 210 degree set point. And again all combinations vary greatly, so to make a generalization I guess would be unrealistic. That said, oil does have an optimal operating temperature, and I can tell you it's definitely not down in the dumps at 140. It might work fine, however it could be improved upon.

So yes, mercury marine does know a great deal about their own product. I'm willing to bet they have a decent relationship with an adviser who likely works for ExxonMobil or shell who looks at the design and proposed use and let's them know what works best with regards to oil, temps etc...

Btw it's all good. If somebody has good luck using a certain approach, why fix what isn't broken. Cheers

My line is good to go, can blow right through it. We just think the bypass is such an easier path that once the block is full and adding resistance all the water just flows through all the 1 inch hoses and out the exhaust. Have lightening headers with dry tails, so all of that flows water with little resistance.

yes youres is the funny looking thing that necks down like a bottle on back of motor by coolor , that unit comes with two choices of thermostat .this post was for the fellar asking about where his is . sorry for confussion

for this guy