Question on Oil Temps & Coolers
 

Do I need larger more efficient oil coolers?

Merc 500 EFI's, with Merlin Heads, 741 Crane Cam, 9.25:1 Compression, dyno'd at 590 HP.

Engines in stock mode ran 190 degrees on oil temp even for extended WOT runs. After the above modifications I am usually at 215 to 220 degrees and it will rise a little to 230 / 240 degrees on WOT runs.

I have always ran Mobile 15W50 oil with good results.

Would like to cool the engine oil temps back down.

Any suggestions would be appreciated.

Re: Question on Oil Temps & Coolers
 

bigger cooler... but i think your ok at that temp?

Re: Question on Oil Temps & Coolers
 

Leave it as it is. Oil has the most lubricity at 200 degrees. The fact that you run at 215 to 230 is good. Since your oil is above the boiling point of water you won't be getting condensation in your oil. Oil starts to break down when it climbs to 300 and beyond.

Re: Question on Oil Temps & Coolers
 

Dock, I believe you are fine with your posted temps. Someone posted a merc bulletin a while back that stated 300 degrees at the sump was the limit. That's considerably hotter than I would run mine but they say its acceptable.

Re: Question on Oil Temps & Coolers
 

Thanks for all the replies.

Guess I will leave well enough alone.

Re: Question on Oil Temps & Coolers
 

I have to agree, these temps are great! Theres a lot of people that would kill to have temps like that. :D

John S.

Re: Question on Oil Temps & Coolers
 

Okay, on another forum a guy asked what my water pressure was.

At WOT I am close to 25 PSI on both engines.

This was his response:

Ok I think you need bigger coolers. Thats allot of pressure.

How will pressure effect this in your opinion?

Thanks
Dock

Re: Question on Oil Temps & Coolers
 

My oil temps went up, when i bumped my rpms up with the upgrades similiar to yours dock, especially at WOT. I get in the 250 range when running 5500-5600. I tried some props that were too big, and wot was 5000, oil temps never rose above stock temps, so i guess the added rpms are a big contributer to the heat..