Highest OIl Temps that are safe
 

The question is what is the highest oil temps that oil can take before issues start?

To start with had a 18 inch long 2 inch diameter cooler and had no idea what the oil temp was. After a short time I wondered why the oil was so black and was running 20W50 Caster oil. Also had 3/8 ID oil lines and standard Merc oil filter block adapter.

This year, installed 10-AN oil lines and oil adapter, along with 525 oil cooler, using Brad Penn straight 50W. Pressure after getting to or above 220 degrees I'm seeing 70 to 80 psi oil pressure. My 530 HP motor is at 220 degrees running 3400 rpm's and gets to 240 degrees at 3600 rpm. When I go higher and at WOT it just keeps climbing. Did not do a lot of running so this was just initial readings with a 18 mile round trip. This was 9 miles up, stop swim and later come back. Water temp is around 85 degrees so its still a bit cool.

Plan to install AFR meters to check ratio, and also water pressure gauge in the block to make sure water is flowing. Also plan to go back to 20W50 Castor oil. Have brand new impeller and Hardin Marine SS water pump housing for this season

Why are you running straight 50w? Engine specs? Bearing clearances?
You might just be creating a s#itload of shear heat in the oil.

straight 50 for a 530 horse engine,please tell me why you feel the need for 50 wt oil.

Where are you reading temps?

I would can the 525 cooler and go with a larger aftermarket

How big is the 525 oil cooler ?

BTW: Carb tune (A/F ratio's) can have a huge impact on oil temps. So, I would wait until you get that dialed in before spending more on parts.

After build was running 20W50 but was only reading 25 psi and would dip slightly lower when coming off plane. Working with another it was decided this season to try 50W to get the pressure up. Installed a mechanical gauge Tee with the electrical gauge. Found a 15 higher reading with mechanical gauge, so figured a 100 psi sender was installed instead of an 80 psi one. Installed a 80 psi gauge and now the gauge reads within 2 psi of the mechanical.

With the gauge offset issue discovered and pressures running so high I'm changing back to 20W50 before I take it back out. Going to reinstall O2 sensors and measure AFR to determine if this is also an issue.

Reading temps at the filter head before the cooler

The old cooler was 2x15 and the new is 2x21 and looks like this one

[ATTACH=CONFIG]567703[/ATTACH]

Technically, a straight 50, and 20w50, will have the same viscosity at 212*. I've ran both , and never noticed higher oil temperatures with straight 50. I doubt thats the issue.

I definitely would make sure it isnt running lean.

Also, what are you running for water thermostat, if any, and how hot are the water temps? Are you running a crossover? What size hoses are feeding the exhaust manifolds? The biggest oil cooler in the world, wont cool well if it doesnt pass much water thru it. Whether thats from impeller issues, or, restrictions after the cooler, like running small lines to feed the exhaust manifolds.

Going to 20W50 right now so the cold start up will be easier. If things start falling in line and get things where it needs to be, might go to Brad Penn 40W.

The motor is running the standard cooling hoses and does not use a crossover. Have a 140 degree TS and motor runs at 160 to 170 at cruise speed. At WOT for some time it doesn't go above 175. Have a water pressure gauge coming in to attach at the block drain plug.

There is no TS in the oil cooler lines

The motor (MPI) was tuned using AFR originally, but going to check to see if things have changed. If 250 or 260 degrees are fine then I'll pay more attention to other things I'm working on, but other threads lead me to think something may be wrong.

Wonder why its running 160-170 water temp, with a 140 thermostat. It should be running, well, around 140.

Its sounding like your high oil temps, may be due to water flow issues .

I personally, would not run my oil at 260 degrees. When everything is right, your oil temperature, and water temperature, should stabilize, no matter how hard youre running. Ive ran in some runs where for 30 plus miles at 5k rpm or higher, my oil never went over 200-210. I only have 8 plate coolers with 800hp engines. Most suggest a 13 plate cooler for that, but i believe what helps me, is i dont run water stats, so the block is doing some oil cooling, and i have lots of water flow, with good water psi at high rpm. Now, that 8 plate, might not get it done, if i restrict water flow, or stick a 140 stat in the engine.

Most of me wishes I didn't change the seawater pump this season to the Hardin. I'm changing to many things at one time and then discovering new things which then cause me to wonder what else could be going on. If I never installed the oil temp gauge I would never know my oil was getting to hot, the previous sign was that the oil was getting black quick.

Note, this is a heavy cruiser so the motor is working had all the time

Temps before cooler are 220-230? That's normal it seems to me... I was told 230-235 max AFTER cooler is the max... that gives you normally a 50 degree drop...

Quote to me when I asked about mine from a respected builder on this site

"I read the temp going into the engine. If you read it before the cooler, You are taking the cooler out of the equation. If you have a small cooler, the temps will be higher than if you have a large cooler. I want to know what the bearings are seeing. I don't want to see over 230-235 deg. That would put it near 300 before the cooler. A conventional oil will start to break down at much over that."

700sci and 600sci specs. Take a look at the max oil temperatures.

Id like to think, that Mercury Racing, has done a little bit of homework on their high dollar engine packages. What their reason is for limiting oil temperature, I dont really know. Whether its life of the oil, cooling of internal engine parts, or what. But for a guy like me, who doesnt have a multi million dollar R&D department, I take some of their recommendations seriously. Definitely would take what they do, over what I read on the interwebs.

If I'm getting a 50 degree drop then 185 sounds good, but this is early season and the water will get much warmer so still need to get my temps down I'm thinking

MT, agree you have much more power and as you say your staying lower then me. Sure hope I don't have to change out the Hardin pump, bad enough to change impeller every other year hanging up side down

Not sure if that was for OP or me, but My info came from Eddie Young just so I don't get bashed for posting what I was informed . In my case in past I would see 150-200 after cooler, but had a hard time in coolerbwater after a richer tube, so I added stats this season now see too much temp, 230 after cooler and climbing... so yesterday inremived them, hence why I asked Eddie his opinion just one of many.

Oil temps in the pan are the average of the oil temps seen in the motor.

A long time ago, a test was set up with a SBC to measure oil temp at the bearings and various other places. They found that bearing oil temps where 60*F - *75F hotter than the oil temp in the pan.

So, this is why some prefer to measure oil temp in the pan, again because there is a reference to go by using this method.

Bearing material and oils used at the time (I believe before synthetic oil was widely used) where considered and a general guideline of target oil in the pan temps was created + generally agreed upon.

The following charts (engine + trans) are pretty much based off of that.
http://performanceunlimited.com/documents/img104.gif

That said, there is reasons why some suggest to read the oil temp after the cooler.

One of the largest reasons why I believe this is / can be important is because of being able to see your oil temp going into the motor when you are going to run the engine at high rpm. Most agree that min oil temp going into engine before running WOT for most motors is 160*F-*180*F.

With just using oil pan temps, you won't know this unless you 100% know what temps your cooler is removing.

Appreciate it guys, could figure a way to measure temps after the cooler, but in any case with current temps it appears I have another problem to solve. Just changed the oil to 20W50 and the cold oil pressure is slightly lower then with 50W.

Is this recomended temp taken before, or after oil cooler?

Caster oil?
 

You are using castor bean oil? Not a good choice for anything except a racing engine where you change the oil before every race.

Its hard for the average DIY guy to find out these kind of answers. Eddie might say 230 AFTER the cooler is ok. Bob Teague, says much cooler than that. Im sure that if you got 10 welll known marine engine builders to give your their thoughts, you'd get 10 different answers on the topic. Then theres the oil guys. They also will give you different answers.

Eddie is much smarter than me, and does this for a living. 230 AFTER the cooler, seems pretty darn hot to me. But again, he is a pro, I am not.

I'd imagine that if the oil AFTER the cooler, is 230, it has to be quite a bit hotter BEFORE the cooler. How much, IDK, prob depends on the cooler and rest of system.

All i know, is that the hotter the oil gets, the viscosity plummets. A 20w50 at 230-240 degrees, is prob like running a 5w30 at 180-190 degrees.

not one Merc small blocks and down run a motor oil cooler ever for a stock app. Even the small block HO MAGS do not use oil coolers. Their oil temps after hard runs are over 220 degrees without any problems and some of the 350 small bocks have 1500 hours on them and or tow skiers around all day long every weekend in the summer.

Texas has very high water temps and high air temps for summer boating. The inboard ski boats - that totally enclosed engine box in the middle of the hull allows no air period to any part of the engine including the oil pan Zero. They get hot running and their oil temps can get very high from lugging skiers around all day long. They do not have motor oil coolers either. Just saying and live very long. The motor oil has to reach 212 at some point to burn off condensation from combustion.

230 MAXED oil temps is not too hot

also other factors turn oil black as well - fuel mixed in to the motor oil, vacuum leaks, and lean conditions all can turn motor oil black as well.

Maybe your motor oil cooler has a form of restriction impeding waterflow Or your water circ pump is not up to par. Seen many of both

how about your t stat and if applicable the check balls and or check valves at any location in the cooling system.

I really do not even know what your app is but throwing the norms out there

383 stroker Mercruiser and I think 400 hp and does not use an motor oil cooler - This is from their repower division

http://www.marineengine.com/parts/me...-3-point-drain

At one time Merc had a 383 - 6000 rpm engine with 450 hp and it had no motor oil cooler on it if I stand corrected.

The 320 efi small block did

300 Tempest had an oil cooler.
https://www.marineengine.com/parts/m...er-and-adaptor

I knew someone would bring that up like us old timers.

That is correct on all 80 of them that they sold back in 1987 thru 1989. haha

It was a combo power steering cooler and motor oil cooler in one unit === Half and half. and not very large either,

Also they used the oil pressure sender on the oil filter adapter mount and the old 2 wire version if I recall correctly for the 320.

Yes and what Mercrusier found thru Merc racing was the Small blocks oil temps were too cold in northern climates with colder water temps. SO no oil coolers because it did cause oil related issues and warranty issues as well.

Merc tracks its warranty claims per sections of the USA and other countries. What issues take place in AZ might not be the same in Canada or Maine or very Northern Michigan and so on. And vice versa.

To add these can be the hottest running engines - the marine gas CAT engines --- because the cat need to have 650 to 800 degrees to be effective and operate correctly. So lack of cooling and heat soak can cause very high heat. These do not have motor oil coolers either. Just saying

http://www.marineengine.com/parts/me...g-system-bravo

Lol was there even 80 of them?

I know but I wanted to say 40 to 60 but thought someone would jump me for that. My best guess seems like 50 to 75 range.

page 33 Max allowable oil temp 284 F

also I have the current Merc Racing info for the 1350 they list the same allowable oil temp at 6500 rpms --- 284 F

page 33 here in the link for the 1075

https://www.scribd.com/doc/101451908...-Owners-Manual

No check balls in the TS housing. Seawater pump is the Hardin pump and new this year.

Also need to get my pressure down below 80 psi

Good info BUP. Thanks.

I want to add the term "Max Allowable" does not mean that you want to be there routinely.

being that he is seeing 240* cruising along at 3600rpm, with a 530hp engine, sounds to me like he is in need of some cooling help. As well as running a 140 water stat, and yet his water temps are 170..

Just my two cents, I would check your oil level relative to crankshaft, if over filled you will whip the oil with the crankshaft causing high oil temps, also I would also check the oil bypass valve make sure you have the right one because that will bypass oil filter and oil cooler if it's the wrong tension. I believe the marine version is 18 lbs.
Good luck

I believe everyone uses the 30# spring in marine engines. I just plug it though.

^^^^^^^ Yes it is 30 for the valve not 18 --- and Merc does state this in a few of its service manuals. ^^^^^^^^

Maybe look at water flow volume to see if its providing enough cooling water.

You have over 80 psi for oil pressure ? Too high is not good either. cavitation in the oil pump can become an issue with too high oil pressures.

Also to high pressures in some cases can also be related to a form of restriction

Oh I thought this was WOT temps and IMO sounds like not enough cooling water volume or inadequate part(s) related for the cooling system to me as both are higher ( water temps and oil temps)