Anybody use Shell Rotella T1 SAE 40 in boats?

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Hey everybody - So our family has a 2007 Mercruiser 4.3 that I was asked to get oil for. My father in law said that he talked to the guy who rebuilt the engine and he said to not bother with getting 20w-40 mercury oil and to buy a good straight 40. I found a decent price for some Rotella 40 and wanted to ask if any guys use this for their boats and if it is a good product. I know the 15w-40 is widely accepted as a good oil and many use it in their boats but what about the straight 40?
 
I don't see any reason to use the sae 40 when the 15w40 should be available at the same price.

What is the minimum temperatures your engine will start at? Sae 40 is fine for summer starts if that's all you have on hand but is it any cheaper than Rotella 15w40?
 
Mercruiser's own oil is multi-weight. I would get Rotella T 15W40. The 15W40 and 40 will be the same viscosity at operating temp, just the 15W40 will flow better at startup. I do not see any reason to use a straight weight oil. The guy who rebuilt the engine may know machining but doubt he is an oil expert. Why did it need rebuilding? Most boat engines fail from water intrusion.

I would break it in carefully. A rebuilt engine is not the same as a new engine as far as breakin. Change the oil once or twice in the first 10 hours.
 
T1, being a Detroit Diesel approved CF-2 rated oil, will have a very low TBN (acid neutralizing capability) which is a bad idea in a marine environment with ample moisture always around. Unless you're running a 2 stroke diesel, I would stick with a 15W40, it'll be usable (& protect against acid corrosion) longer.
 
AGREED, the tbn is kind of wimpy

http://www.kellerheartt.com/v/vspfiles/Data%20Sheets/Shell%20Rotella/GPCDOC_Local_TDS_United_States_Shell_Rotella_T1_40_(CF_CF-2)_(en-US)_TDS.pdf

go for a CI or CJ 15w40
 
The >$1M sportfishing yachts we ride (and sell oil to) often want SAE 40. But theyre running in 80 degree water, high RPM cruise for extended time, then LOTS of idle.

For a smaller more transient use engine, Id use the OE viscosity. The big diesels in the yachts I speak of likely spec a straight weight amongst others as acceptable. What does Mercruiser spec?
 
So this boat is used in Lake Placid only during the summer. it is shut down by Labor day. It would be used to water skiing and general boating, nothing crazy but lot of high throttle situations. The spec for the engine is 25w-40 Mercruiser oil but considering it's my father in law I didn't want to disagree. He isn't the type that takes kindly to being told what's right haha. I thought the 15w-40 would be better for this application and probably cheaper. I wasn't sure if it was going to be unsafe. Sounds to me like having a low TBN we will have to change it yearly anyways.

The boat wasn't properly winterized a couple years ago caused some internal issues which I do not know 100% of the details as to what. The rebuilder did bore out the cylinders and put in a 4 barrel carb and told him that as long as we aren't using the boat during the early spring/fall that straight 40 is fine. Just change it yearly. I think for this application it might be OK but the 15w-40 would be good if we end up not changing it every year. Knowing my wife's family this might be the last oil change until the rapture. Thanks everybody for the good information!
 
In my 4.3 Merc, I use straight 40 Rotella that was given to me dated 2004. I have used it for the past 11 years no problems. There is never any sediment at the bottom of the bottle after filling. I have 7 gallons more of it, so I have 7 years left of using it. After that I will explore multi grades. BTW, this boat has 2600 hours on the engine and was rebuilt by me at 2050 hours out of precaution. The rings and bearings were hardly worn. This boat was purchased by me new in 1996 and has seen nothing but 40wt Rotella or Delo. It is what the owners manual recommends (as well as Merc 25W40). I have other boats that use different oils, but the 4.3 never skips a beat on straight 40wt.
 
There are some "Best SAE 30" and SAE 40 threads over in the automotive forum. Go read through that stuff and make your own opinion... If the lake is not frozen, the bilge temp is high enough for SAE 40. There is some evidence that straight SAE grades do a better job of protecting the upper cylinder wear that multi's. And this is an area that can be compromised by having one valve open to the wet exhaust on shut-down...

Many marine applications run straight grades. And if you want TBN, MobilGard (dedicated marine oil for the shipping industry) will give it to you in spades - TBN starts at 15. You'll have to find a dock service company that will sell it to you in less than 55 gallon lots though ...
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This is an industry I worked in for decades. Straight SAE oils are the norm, not the exception. They are tough. they have zero VII's to shear down under high load. They keep a lot of engines running for 10's of thousands of hours.

Also, many light aviation engine MFG's and reman shops (another engine that runs at constant load and throttle) require the use of dino oils in straight grades. Multi's can be considered after the first three oil changes...

You absolutely will not hurt that engine on straight grade oil.

We ran it in the big Olds powered jets for ever. And a lot of serious ski boats run straight grades...
 
Thanks everybody for the information. Boats and Marine engines are not my strong point. I figured it wouldn't be an issue for the boat. We are going to be changing it over the holiday. I'll get back to everybody when she is purring like a kitten.
 
Go with Broc's recommendation. From what I've read of his post, he is experienced and well educated in the boat and industrial sector. He has been making very strong and intelligent points as to the strength of monogrades as well. All I can add is that when shopping HDEO monogrades, you're going to want a CF rated lube, not a CF-2, as the latter is for Detroit and MTU two strokes.
 
Originally Posted By: bullwinkle
T1, being a Detroit Diesel approved CF-2 rated oil, will have a very low TBN (acid neutralizing capability) which is a bad idea in a marine environment with ample moisture always around. Unless you're running a 2 stroke diesel, I would stick with a 15W40, it'll be usable (& protect against acid corrosion) longer.


You stole my thunder, my answer was going to be that I'd absolutely run T1 40wt in a boat... Provided it was powered by a 2 Stroke Detroit Diesel. The T1 also has very low zinc.
 
30 years of Merc 25w40 in all 7.4L big blocks
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....run wide open all day and idle for hours. Change every 50 hours.
 
Anyone know zddp level for Rotella T1 sae 40? Used it in my Bayliner. Seems ok. Mercruiser 3.0 that oddly specs CF/CF-2 for a gas engine.
 
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Like I said above - straight grades are the norm. I might not lean to Rotella T1. I might pick another SAE40... But it is the norm.

Sure many of you'all have had great success with Mercury Quicksilver 25W-40. It is a great oil. One of the best multi's out there. And I would not feel the slightest hesitation in running it in any modern 4-stroke marine engine. But that is not what the OP asked ...

He asked if 40 was OK. It certainly is, and is common. Is it the best? That's debatable as we have seen here in discussion ... But you can't kill a Mercury Marine engine with a 40. Lesser oils maybe ...
 
All the shops around in area use straight 40 ,1540 or 2050.

We have bath water temps on a lot of parts of our lake.
 
The Detroit Diesel lubricant manual doesn't specify a zinc requirement for the CD/CF/CF-II oil but does recommend a minimum of 700ppm. Limit for Sulfated Ash is 1.0%.
 
Originally Posted By: BrocLuno
Like I said above - straight grades are the norm. I might not lean to Rotella T1. I might pick another SAE40... But it is the norm.

Sure many of you'all have had great success with Mercury Quicksilver 25W-40. It is a great oil. One of the best multi's out there. And I would not feel the slightest hesitation in running it in any modern 4-stroke marine engine. But that is not what the OP asked ...

He asked if 40 was OK. It certainly is, and is common. Is it the best? That's debatable as we have seen here in discussion ... But you can't kill a Mercury Marine engine with a 40. Lesser oils maybe ...


Interesting Conversation everybody. I appreciate the feedback. We ended up using the Rotella 40 and it seems to be working great. I am going to plan on changing the oil at least once a season if not every other. it is used hard but probably used a total of 3-4 weeks from memorial day to labor day. Not for long hours. I think next time around I will go for any of the HD 15w-40s that is on sale. Seems like any of the big 3 will do just fine
 
I've used Delvac 15W-40 in my 3.0LX gasser since new in '96. One year I did go with a straight 40W and noticed that the oil pressure was higher at idle and when first starting out. One thing to keep in mind about straight vs. multiweight, is the actual thermostat opening temp. Mine is 160 so that oil never really got hot, and I think that's why the pressure was higher. Switching back to the 15W-40, pressure went right back to where it had been her whole life. I can imagine the waters at Lake Placid are way cooler that down here in SW Oklahoma in August though.
 
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