Oil temp high
 

Hello all.
new to owning big blocks.. had all 350s.
I recently bought a Sunsation with 502 bored out to 509 and dyno for 550 hp. I ran boat yesterday on lake st Clair and was seeing idle oil temp 230, 3000-3500 250-255 3500-4000 260-270. Water temp stayed steady at 160-170 degrees.

Called previous owner and he stated all oil temperatures is what he would see. When WOT I should see 300 degree.

Looking for guidance on if this normal range? I’m using 20w50..

That's very hot for my big blocks. In my experience anything over about 240 degrees starts to have an adverse effect. Oil should be around 200 at full temp and hard usage can see 220-230 but 250+ or even 300 is really hot. Oil needs to get hot enough to evaporate moisture and do its job, which occurs around 200-215 degrees. At 240+ it's going to break down and not be able to do its job.

thor Thanks for your reply. If temps are that high, could it indicate I need a replacement oil cooler? I personally do not feel comfortable running even 240..

We don't have a "performance boat" per but do have a 7.4 mpi- What you reported is a little warm for oil temps. Thor39 I believe is correct that at 240+ the oil most likely will start to break down. Years ago we had a 165 hp Straight 6 and was running it very hard on a VERY hot Labor Day - the engine temp stayed cool. All of a sudden the engine oil light came on and the oil pressure dropped. I immediately shut the engine down- the oil was full nothing out of the ordinary. Took the boat to a local marina and was expecting the worse - We ALWAYS ran 30W Strait Rotella in this engine from day 1- Turned out the oil broke down and couldn't maintain pressure - we switched to 20W-50 and the engine just purred. Your engines probably have oil coolers - Is it possible that these have become plugged or their internal thermostat isn't opening/closing as it should? I'm not a mechanic but I would start with the simple stuff first and then go from there. All the best

3pointstar

If that was after the cooler I'd be really concerned. But before the cooler it would be something to monitor. I know the boat is new to you and you don't know what is normal. (do you trust the previous owner) I'd pull the oil filter, cut it open and inspect the pleats. If it's clean that's a good start. This is a highly debated subject here. There is the thought of monitoring before or after the cooler. I personally want to know temp after the cooler and what is being delivered to my engine/bearings. Others talk about it needs to be measured in the pan. (who cares what the pan temp is...) Oil sees extreme temperatures in the cylinders and 350+°F on the valve springs. Just look at the color valve springs turn (you know they are over 400°F) and oil is the only cooling they receive. Just too many variables. If concerned install a larger cooler. The best thing is to know base lines and go from there. Differentiation from normal is what you are looking for.
my $0.02

3pointstar what a fortunate break you had there! Oil cooler is real simple to get to. Thank for the advise. Hopefully it’s a simple clog but only time will tell.

Had the same issue until I changed the size of the oil cooler after repower. If you have the standard 502 oil cooler then your going to need to get a bigger one. Mine was about 8 inches long and mounted on the port side of the motor. Wound up getting a 2/75 by 18 inch cooler which took care of the issue. Probably should also install a oil thermostat b\ut that's another day

https://www.offshoreonly.com/forums/...ps-safe-7.html

Is the gauge right? Right senders in there?

Seems pretty hot

Locked one up running about 260*. I was running down the river hard, then just cruising about 3500 rpm.....no knocks a couple tics from the lifters and seized up. Temps always came back down to around 200-215 once I was out of the throttles. Maybe I lost an oil pump, Idk... But it def took me by surprise.

Maybe a larger oil cooler, or larger pan is in your future. Perhaps both...

the size of the cooler lines also comes to play,i like -12 but -10 will work.the stock merc lines are maxed out on a hp500 that is stock.

What was the engine originally?? 502Mag or HP500?? Did they upgrade the oil cooler??

lake st.clair,,,where i boat,,,
i was running high temps 260ish,,,machine shop didnt seem to think it was too hot,
but had to pull motors to address water pump changes, i updated oil coolers with big
CPH-700 Thermostatically Controlled Cooler 3 inch bundle,from mr cool
now motors run 200 -230

high oil temps - high volume oil pumps
 

Any idea how much a high volume oil pump may raise oil temps , compared to the std oil pump??
I have a stock 1998 415hp 502mpi just with Eddie Marine exhaust and some advanced timing at WOT to 36 deg.

I like simpler the better. I am trying to run without all the remote filter setup, oil cooler, hoses, which adds weight and takes up room, and potential leak spots. Often hearing these stock motors dont need the high volume pump, just the standard unit.

I'm hoping that with doing a couple other things like lower the timing a couple degrees, and checking for lean AFR, that i can run without a cooler/remote filter setup.
Oil temps running a little high, 280F cruising just under wot.
I like the oil a little hot to keep the oil as dry as possible. Would like around 250max running hard, over 200 cruising easy.

what engine(s) are you running? Overwhelming response are indicating oil cooler - I’m going to purchase just need to find correct one for me..

502 mag. Didn’t upgrade oil cooler

I am having the same issue with hot oil, I have cleaned coolers and replaced water pump. I too am starting to believe it is the actual size of the cooler. I run the same 20-50 oil but if i run with or without an oil thermostat installed, my temps are climbing to 280 on a 4000 rpm run for 15 mins. Im not trying to hyjack your tread but have been battling this since i got the boat last year. No thermostat in engine with a cross over and never see my water temp gauge move. Took a test ride today in 45* water and after 30 mins still saw 280 on the gauge. Im going to measure my oil cooler tomorrow. What size did you end up going with? Never had any problem with the engine but still concerning when your oil temps rocket, water pressure is considerable low at 5 psi while cruising and then not seeing any water temp. Hard to really tell condition of what is happening. Im assuming the low water pressure has to due with the fact of not running a thermostat with the crossover, but worried about adding restrictors in housing to boost pressure and then have my oil get even hotter with less flow of water.

What engine and specs? Custom build? Sounds like you might be bypassing the cooler. Do you have the marine heavy bypass valve in you oil filter pad, is it plugged or the light automotive bypass?

do these and be done with it, if you get it wrong it's only your motor.
https://www.hardin-marine.com/p-1097...ing-mount.aspx
https://www.hardin-marine.com/p-1097...rmostatic.aspx

Its a Mark IV Dart 555 block, Brodix Aluminum heads, brodix hvh intake and quick fuel 1000 carb. All raw water cooled. Was told makes around 750 HP but have no actually specs on that. Where would that be ? Inside the filter mount? So you think it’s not pumping though the cooler at all? Compared to what GLENAMY just posted my cooler is not nearly that big. I have to write 10 post before i can submit a photo.

You need minimum 3x18" CPH-550, CPH-700 if you want thermostat. Russ usually gives an OSO discount.
https://www.mrcool.us/coolers/hi-per...e-coolers.html

It’s already been said, High AFR’s will make high EGT’s and cause high oil temps. That Hardin cooler keeps my 540 under 230* and I have closed cooling. Good luck and safe boating

Yeah just took a measurement on mine , the cooler is 3x16 and that’s from threads to threads so actually cooler tube is only 12 inches. Now that I’m typing this and reading it out loud that seems way to small, for what the motor is putting out. Even with all thermostats removed.

That would be the issue. definitely needs a larger oil cooler.

3 things come to mind before you condemn the oil cooler/lines as being too small
1. Is gauge actually correct, you can shoot a infrared gun on dark areas on pan, cooler, fittings and see IF its close to correct, surface temps will read 20 to 40 less than actual
2. IF a high volume pump is used and a std bypass valve was put in block by accident, its possible to have it open and bypass hot, unflitered oil to your motor
3. as mentioned, if your running too much timing or lean afrs, alot of heat will be created and transferred to the oil

Are these coolers just more efficient than the stock Mercruiser stuff, or are these being used as a secondary cooler? I replaced one of the factory coolers a couple years ago, do to a crack over the Winter. Was nota Merc brand, but looked just like it. Does the same thing as others here, run it hard for a few miles and the oil temp heats up. New sea pump impellers do not make any difference.
BTW, my oil temp sensors are on the remote filter mount.

No to both
Your motor is producing more heat due to the increase in hp. The old cooler was designed to meet the minimum needs to meet the original motor build. Your new motor probably has a high volume oil pump (do verify and see if bypass valve has been plugged) and therefore it needs larger oil lines and cooler.

If you look thru my thread in previous post it will show what I went thru to get my heat down. You may not need to do all of what I did, and may need different things, but its one look at the issue and the process

Please excuse this question, but are you referring to the bypass that would be in the adapter or in the remote filter housing? I run a Wix 51649 filter without a bypass in the filter, if that changes things?

The valve is located on the block where the filter would attach or where the remote oil filter attaches. Mine was removed and plugged

https://www.offshoreonly.com/forums/...safe-oil-2.jpg


https://cimg5.ibsrv.net/gimg/www.off...b692085726.jpg



https://cimg4.ibsrv.net/gimg/www.off...39fb91a3ff.jpg

my motors are 547"s...
my oil coolers wont open till 210 temp,
posted num,ber for them,,,

Before you buy anything shoot it with a temp gun.

this is what works great on my 557cid/650's. hardin thermostatic filter mount and 3x20 oil cooler. simple setup and i can run hard and never see my oil temp over 210.
https://cimg1.ibsrv.net/gimg/www.off...bbfb6b1f76.jpg

For those that have larger cooler, are you running a standard single stage mercruiser water pump?

Yes, Standard pump

Yes, single stage here

I run the 3"x18" earlier mentioned. 454's 600 HP. Similar mounting as Saber28. I don't see temps over 180°F
.
https://cimg6.ibsrv.net/gimg/www.off...30278f51f8.jpg

So looked at engine and checked oil cooler no clogs. Oil cooler is standard 502 2x12 and goes to power steering cooler. I have never ordered an oil cooler so looking for more guidance lol.. teaching myself. Anyhow, 502 gen v 550 hp.. help, please :-)

If you can be sure the cooler came off a working motor without a failure then you can get a used cooler. If the motor had failed prior, there is no kind of flushing other then to take apart to ensure all the metal has been cleaned out.

Opinion
If you can find a good used 2 3/4 x 18 Merc 500 cooler it should work just fine without a thermostat. If you get a larger one and do not have a thermostat then the oil can stay to cool so moisture may not be removed during running. Can get a larger one with a thermostat so the oil can reach at least 212*

BS DON"T buy a used oil cooler, people actually lie about the history of parts. It's your engine do as you please. I have already posted links for the correct oil coolers, do as you wish. Good luck with used metal particles in your oil!

GLENAMY- i definitely would not buy used. I actually went back and bought the oil cooler you mentioned. I appreciate you commenting and adding the link! Hopefully this $1500+ investment gives me 210-220 temps!!

BS please read the Fing comment
Mine is used and came from a OSO guy I trust, and has been working just fine