Whats TO HOT FOR OIL TEMP
06-24-2014 | 08:13 AM
#11
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From: Gaylord, Mi
I have mercury oil thermostats. I see about 180 cruising and 210* at WOT. Running a 10 quart pan, with plate style oil coolers. Ive tested the merc oil stat element in a pot of water with a thermometer. At approx 180, the element is starting to open, by 200ish, it was fully open.
I see alot of stuff on the net claiming that certain race teams and oil brands talk about 300* oil temps. Keep in mind, these guys running the oil temp that high, are keeping it in for 1 race. My oil stays in my engines for 10-15 hours, and my bearings stay in much longer than that. i dont plan to tear my engines down every other boating weekend. So what those guys get away with doesnt really relate to my boat engines. 200 degree oil flows almost like water. 300 degrees, its gettin pretty thin.
I'd like to see how long a semi truck, pickup truck, or even daily driver would hold up to 300 degree oil sump temps regularly. Most vehicles are designed to have oil temp relative to engine coolant temp, (190-210*). I personally would never want my oil anywhere near 300* sump temp. Localized temps can be much higher.
I see alot of stuff on the net claiming that certain race teams and oil brands talk about 300* oil temps. Keep in mind, these guys running the oil temp that high, are keeping it in for 1 race. My oil stays in my engines for 10-15 hours, and my bearings stay in much longer than that. i dont plan to tear my engines down every other boating weekend. So what those guys get away with doesnt really relate to my boat engines. 200 degree oil flows almost like water. 300 degrees, its gettin pretty thin.
I'd like to see how long a semi truck, pickup truck, or even daily driver would hold up to 300 degree oil sump temps regularly. Most vehicles are designed to have oil temp relative to engine coolant temp, (190-210*). I personally would never want my oil anywhere near 300* sump temp. Localized temps can be much higher.
06-24-2014 | 08:13 AM
#12
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From: Newark, DE
2 things I was told about oil temp, 1. don't run it hard untill you at least see 140 for oil temp, and 2. you want your oil temp to at least get to 190 to burn off contaminants and condensation. According to the chart it is saying you want to at least get to 175 for oil temp to burn off contaminants and condensation.
06-24-2014 | 08:21 AM
#13
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OK So is the 225-235 that we are running to hot? i get so many different opinions im not sure whats correct. when im running the boat when i see the temp get this hot i get nervous and i wont run over 45 mph or i slow down to an idle and let everything cool off. If it is to hot whats my next step to cool it down, already have an oversized oil cooler, Is my problem the cooler not getting enough water, with my intercooler and extra hoses robbing water with a stock water pump, should i try a larger one ?
06-24-2014 | 08:29 AM
#14
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From: AZ
Some food for thought here. Mercruiser and Hardin seem to prefer a 210 degree thermostat in the new oil adapters they are currently using. It makes a lot of sense to get the oil temperature up not only to avoid extra wear but to also burn off moisture. After much research I opted for a 215 degree thermostat with my heavy duty teague cooler. The reason I chose this was two fold, one a tribologyst recommended it,(works for a oil company that's heavily involved in all aspects of motorsports including race/endurance boats)and two water boils at 212 degrees. I always run redline synthetic which is a very robust oil, so if I were in the high 200's it's of no consequence.
If you are worried about the viscosity of your oil with these higher set points, keep in mind it might seem like its "flowing like water", however motor oil is tested at 100 degrees Celsius, so your 10w-40 for example is performing as a 40wt inside of your engine at that temperature. The physical viscosity of the fluid doesn't magically thicken to a heavier grade, so don't let that confuse you. Shear is what you want to look at in this case. All oils shear down in grade from use, however some shear very little. A big block Chevrolet is a very low shearing engine design, so that leaves fuel dilution as the number one reason to change your oil, followed by additive package replenishment.
If you are worried about the viscosity of your oil with these higher set points, keep in mind it might seem like its "flowing like water", however motor oil is tested at 100 degrees Celsius, so your 10w-40 for example is performing as a 40wt inside of your engine at that temperature. The physical viscosity of the fluid doesn't magically thicken to a heavier grade, so don't let that confuse you. Shear is what you want to look at in this case. All oils shear down in grade from use, however some shear very little. A big block Chevrolet is a very low shearing engine design, so that leaves fuel dilution as the number one reason to change your oil, followed by additive package replenishment.
Last edited by Borgie; 06-24-2014 at 08:36 AM.
06-24-2014 | 08:59 AM
#15
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From: chicago
Engineers at mercury aren't dummies. There's a reason they specd the oil stats to open around the 210 range. I believe on the newer merc racing engines the alarm will sound if the oil temp reaches like 220 or 230.
Bottom line is oil breaks down with heat. Synthetics hold up better but still can breakdown.
I've never hurt an engine from running the oil on the cooler side of the scale. 212 is boiling for water. However, put a pot of water on the stove at 175 degrees, and you'll see steam vapors. Point is the 212 number isn't crucial . Most engine oils are designed around a operating temp of 200 degrees.
I'm not gonna get into the debate on oil shearing , oil brand, base stocks, blah blah blah. After several hundred hours the proof is in the pudding. If mercury or any other manufacturer wanted high oil temp, they would design it to have high oil temp , but they dont. I don't hold my engine wide open for a few seconds and let off like a sissy. I wanna be able to hold my ****t on the dash and watch the oil temp hold steady. That's where a good oil stat unit and large cooler come in. But even they can't overcome a poor oiling setup, extreme valve spring surge, or lean fuel system.
As far as the 502mpi seeing 235 deg with 520hp and stock cooler ,.....I would install a larger cooler rather than remove the water stat.
Bottom line is oil breaks down with heat. Synthetics hold up better but still can breakdown.
I've never hurt an engine from running the oil on the cooler side of the scale. 212 is boiling for water. However, put a pot of water on the stove at 175 degrees, and you'll see steam vapors. Point is the 212 number isn't crucial . Most engine oils are designed around a operating temp of 200 degrees.
I'm not gonna get into the debate on oil shearing , oil brand, base stocks, blah blah blah. After several hundred hours the proof is in the pudding. If mercury or any other manufacturer wanted high oil temp, they would design it to have high oil temp , but they dont. I don't hold my engine wide open for a few seconds and let off like a sissy. I wanna be able to hold my ****t on the dash and watch the oil temp hold steady. That's where a good oil stat unit and large cooler come in. But even they can't overcome a poor oiling setup, extreme valve spring surge, or lean fuel system.
As far as the 502mpi seeing 235 deg with 520hp and stock cooler ,.....I would install a larger cooler rather than remove the water stat.
06-24-2014 | 09:04 AM
#16
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From: Newark, DE
Engineers at mercury aren't dummies. There's a reason they specd the oil stats to open around the 210 range. I believe on the newer merc racing engines the alarm will sound if the oil temp reaches like 220 or 230.
Bottom line is oil breaks down with heat. Synthetics hold up better but still can breakdown.
I've never hurt an engine from running the oil on the cooler side of the scale. 212 is boiling for water. However, put a pot of water on the stove at 175 degrees, and you'll see steam vapors. Point is the 212 number isn't crucial . Most engine oils are designed around a operating temp of 200 degrees.
I'm not gonna get into the debate on oil shearing , oil brand, base stocks, blah blah blah. After several hundred hours the proof is in the pudding. If mercury or any other manufacturer wanted high oil temp, they would design it to have high oil temp , but they dont. I don't hold my engine wide open for a few seconds and let off like a sissy. I wanna be able to hold my ****t on the dash and watch the oil temp hold steady. That's where a good oil stat unit and large cooler come in. But even they can't overcome a poor oiling setup, extreme valve spring surge, or lean fuel system.
As far as the 502mpi seeing 235 deg with 520hp and stock cooler ,.....I would install a larger cooler rather than remove the water stat.
Bottom line is oil breaks down with heat. Synthetics hold up better but still can breakdown.
I've never hurt an engine from running the oil on the cooler side of the scale. 212 is boiling for water. However, put a pot of water on the stove at 175 degrees, and you'll see steam vapors. Point is the 212 number isn't crucial . Most engine oils are designed around a operating temp of 200 degrees.
I'm not gonna get into the debate on oil shearing , oil brand, base stocks, blah blah blah. After several hundred hours the proof is in the pudding. If mercury or any other manufacturer wanted high oil temp, they would design it to have high oil temp , but they dont. I don't hold my engine wide open for a few seconds and let off like a sissy. I wanna be able to hold my ****t on the dash and watch the oil temp hold steady. That's where a good oil stat unit and large cooler come in. But even they can't overcome a poor oiling setup, extreme valve spring surge, or lean fuel system.
As far as the 502mpi seeing 235 deg with 520hp and stock cooler ,.....I would install a larger cooler rather than remove the water stat.
06-24-2014 | 09:09 AM
#18
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From: chicago
Yea I would agree with installing a larger cooler. You run a crossover with a bypass with tstat don't you? I have been having a tough time working out water pressure. It sees none ever unless I restrict the water flow through the bypass, that was another reason I was going to go away from the bypass and tstat. By doing that it would take care of 2 things at once lol.
06-24-2014 | 09:34 AM
#19
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From: Newark, DE
I have the one with a 1" bypass hose which is much larger than stock, it honestly flows an absolute ton of water through the exhaust lol. Registering no water pressure on gauge (water line is same place yours is, port side drain on block) with this set up. I can pinch down the bypass hose and get it to register, have to pinch it down a good bit. I think I am going to just block off the bypass and remove the thermostat for now untill I get a bigger oil cooler. Atleast that will get my oil temps down some so I have more head room with temps there
