mercrusier oil for HOT temps

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I live in az where it reaches 116+ outside and will be 100° at midnight during the summer....

I've recently acquired a 85 3.0 and it sat for a bit, I have about 7 different types of oils in it including (dun dun dun, Diesel )just a tad mind you! To clean her up while we get everything in order and set correctly...


Mercury says ( 25w40 for all temp ranges or 40wt for anything above 50°)


Upon research, there's a disgusting amount of people who run 5w30,30, 1040, 0w40 and all sorts other crazy oils for many many many hrs or years and don't have any better knowledge/reason other then (I've never had a problem)


If I use context clues with mercury, it looks like I'm ok with any oil, they even say 20w50 (kinda) ok but its nooooooooowhere near as good as their own 25w40
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Local boat shops say 40 for our waters is what they recommend, and even the local mercury shop laughs at the 25w40 the manual says...

my neighbor does a lot of work on boats and his son is a certified mercury mechanic and he said (20w50 or 40wt and be done with it)

which leaves me pondering the question of (what do I use)lol

anyone have a suggestion? im really leaning towards 2050 but I know how much stronger straight wt is....
 
Originally Posted By: leroyd92
anyone have a suggestion?


Delvac 1300 15w-40 is going for $12/gallon @ WalMart and will provide all the protection you'll need in that carbureted 3L.

With that said, considering we're talking about an '86 here, I'd focus more on make sure the fuel system is clean -- pick up a couple bottles of either Techron or Regane while you're there getting the oil.
 
I was thinking the same thing, honestly, I was gonna feed it to my f150 next oil change.....


The boat needs new flooring, tank will come out, and its drained anyways, the boat has ran off of a 500:1 mix of tcw3 to loosen everything up.... she likes it too!

I think I'll get delvac, just cause. Try it and see how low oil pressure gets during the summer months.... might as well put it in the Volvo 290 while im at it...
 
Any name brand 15w40 should fit the bill. No reason to use 20w50 over 15w40 unless your trying to slow consumption. The engine obviously has a large range for oil choices. 15w40 is just so Stout and readily available it's hard to ignore
 
When we say 1540are we talking about diesel rated oil or regular gasser oil?

I ask, because I've seen diesel oils are rated differently.

And you said stout??? Does 1540 have a high shear resistance ???
 
Originally Posted By: Ramblejam
Originally Posted By: leroyd92
anyone have a suggestion?


Delvac 1300 15w-40 is going for $12/gallon @ WalMart and will provide all the protection you'll need in that carbureted 3L.

With that said, considering we're talking about an '86 here, I'd focus more on make sure the fuel system is clean -- pick up a couple bottles of either Techron or Regane while you're there getting the oil.


+1. Good advice on oil selection. I have tested this engine on 15w40 and mercruiser 25w40, and the mercruiser oil sheered quite a bit in nominal use compared to the 15w40. Used both Delvac and Delo. The engine was a 1998 3.0 carb motor.
 
Diesel oil can be dual rated for gasoline and diesel engines. When I say Stout I'm referring to the excellent additives usually in slightly higher concentration than gasoline only oil plus they should be plenty shear resistant enough for you especially considering you said some people run 5w30 with no issues.
 
Mercruisers don't run HOT. Your 3.0 probably has a 145-150 degree thermostat in it. I run 15w-40 in mine.
 
Originally Posted By: Too_many_Cars
What is your raw water temp temp coming into the water pickup.
Joe


Bath water in the peak of summer
 
And there are lots of spots on the water where the water is as warm as bath water.... if my water was cold I wouldn't think anything of it and sun 30wt... but I've seen how thin oil gets at 200/250/270°like my Harley does
 
Thermostats are typically 165 for Mercruiser. But, that does not mean oil temperature is 165. It can be hotter.
Any dual rated 15w40 would be perfect. Mobil 1 15w50 if you have deep pockets.
 
Water temp determines your engines operating temp more than the air. Also marine engines run cooler than automotive.

Any oil works fine, I have had good luck with the Merc oil, or any 15w40.

I have never seen a marine engine oil failure, your 3.0 is an ancient truck motor I think from the early 70's. Anything is fine in it, a lot of guys run whatever 10W30 is on sale. Also as said above unless you have the run T stat in it or the riser is shot it should run around 165ish.

That's also about where the 4.3's run, while in my truck they run at 210. Big difference.
 
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a water to water heat exchanger is awfully effective. Any normal water temp at the inlet under 100 degrees is likely to keep that engine mega cool and require the Tstat to force it to full temp whatever that is.
 
Our BB's run around 190 deg. In the spring when Lake Erie is COLD we run 170 to 180. I have also have great luck with Merc full syn. We take them apart about every 5 years. The girls look great. We will do the lowers in 2015. Twin 454 Mags
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we like to let them eat at 5500. I know..... Not good for mileage and motors..... But, we love the speed. 80's on the water is crazy in a v bottom. The old Formula is a 2000. Will try to post a photo. Can burn 100 gal quick. It is worse than a bad habit. Heck it is!!! Don't give me too much heck, but we love the speed and sound of this boat. Purchased new. A one owner.
 
Btw. It is 4 deg at Catawba Island Ohio. Lake Erie had the most ice on her in 20 years. Average of 4 in. We came up to check our house. We watched two Chevy pickups go out on the ice. That takes some stones! Not me. I like water that moves and above 60 deg. We were so flabbergasted I forgot to take a photo.
 
My go-fast sliver has a 572 with a little boost thrown in for about 850 hp at the crank. It can really drink the go juice at higher throttle openings but there are few places where it's right for triple digit speeds!

I have a rev limiter that shuts down the fun at 6800 rpm, but my builder swears it would run 7200 all day long.

Engine temps are never over 190 no matter what, I use a tiny little heat exchanger from a Cat diesel catalog...
 
I may be to old for triple digits, but still like the speed. Sounds like a great toy! Love the sounds from the BB large HP.
 
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