# Question about lower unit oil?



## Tim Murphy (Oct 20, 2012)

Dear Board,

I have 3 small outboards that I need to winterize. As part of the process I am going to change the oil in the lower units. The motors in question are a 35 HP 1982 Evinrude, a 6 HP 1986 Evinrude, and a 1997 4 HP Yamaha. I need a bit more than a pint of gear oil to re-fill all three gearcases.

A pint of gear oil in a boating store is $ 8.00 or $ 9.00. I can buy a gallon of 75-90WT gear oil at an auto parts store for $ 13.99. I won't need all of it but I would then have enough left over for several years worth of re-fills.

My question is will I do any harm to my motors by using oil marked for automotive limited slip rear ends? I personally think it would probably work just fine but I'd prefer to have someone confirm my suspicions.

Thanks in advance,

Tim Murphy


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## Johny25 (Oct 22, 2012)

Marine gear oil has and additive in it that does not break down as bad or foam as much when water gets in (and it will get in at some point). Stay with the marine oil. Automotive gear lube will work but marine grade gear oil is better and the correct stuff. Car differentials are not designed to run under water and neither is the oil that is put in them.


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## Charger25 (Oct 23, 2012)

Johny25 said:


> Marine gear oil has and additive in it that does not break down as bad or foam as much when water gets in (and it will get in at some point). Stay with the marine oil. Automotive gear lube will work but marine grade gear oil is better and the correct stuff. Car differentials are not designed to run under water and neither is the oil that is put in them.




THANK YOU , THANK YOU, THANK YOU !! :LOL2: 
When I was in my 20's I had a 17ft ski boat, i was changing the oil in the lower unit and was ready to put in regular gear oil when my neighbor, an elderly but distinguished Gentleman, came over, cuffed me in the back of my head and said " Are you stupid or what ! " #-o Then he handed me a beer and took the time to explain to me the differences that Johny25 has just stated. For all you young bucks on here, take time and listen to the old farts,they will save ya !


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## Tim Murphy (Oct 26, 2012)

Charger25 said:


> Johny25 said:
> 
> 
> > Marine gear oil has and additive in it that does not break down as bad or foam as much when water gets in (and it will get in at some point). Stay with the marine oil. Automotive gear lube will work but marine grade gear oil is better and the correct stuff. Car differentials are not designed to run under water and neither is the oil that is put in them.
> ...



Hey guys,

I hear what both of you are saying, but the fact remains that my Yamaha manual specs 90 weight hypoid gear oil and the Evinrude's spec Evinrude Hi-Vis which according to an old outboard mechanic I know is nothing but straight 90 weight with a fancy label and the appropriate upcharge.

I bought "Marine" gear oil at Wal-Mart which I suspect is neither 90 weight nor actual gear oil but I'll use it anyway and hope for the best. My other options were the rear end oil or fancy synthetic gear oils labeled by an engine maker. Since the synthetics weren't spec'ed it's clear they aren't needed.

The bottom line is that if your gearcase leaks and allows water intrusion then only the hand of God can save it if you aren't paying attention to it. 

I have many years experience in the heavy equipment industry and the only thing that matters is CLEAN oil. Cheap oil maintained at the proper level and exchanged at or before the recommended oil change interval will always provide better protection than the finest most expensive oil that goes too long before a change. Oil never wears out, its oil. Oil does not break down, it does however get contaminated, and that is where the problems occur.

Regards,

Tim Murphy


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## Johny25 (Oct 28, 2012)

Well it is your motor so put whatever you like in it. And I'm not sure why you want to debate the meaning of "breakdown"? But If memory serves me hypoid oil is an extreme pressure oil, designed to handle the high rpms that those gears are going to be turning for long periods of time. So yeah throw some offbrand 80-90w differential oil in it and call it good eh :lol: 

A gearcase is the 2nd most expensive thing to replace on your outboard.... a few extra bucks for the correct oil is well worth it trust me. Buy the exact oil your manual states


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## CaseyP (Oct 28, 2012)

I'm not understanding why you asked the question in the first place if your just gonna go and put the cheap stuff in anyway. Listen to what has been said. Its called marine grade for a reason, its not just some fancy label they put on it so they can charge more. Its more because it for a boat and has additives in it to keep damage from happening to your lower unit when it does leak.


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## JMichael (Oct 28, 2012)

CaseyP said:


> I'm not understanding why you asked the question in the first place if your just gonna go and put the cheap stuff in anyway. Listen to what has been said. *Its called marine grade for a reason, its not just some fancy label they put on it so they can charge more. Its more because it for a boat and has additives in it to keep damage from happening to your lower unit when it does leak.*


I don't know if this is true or not but do you have a source to show this is "fact", or is it just something you read some where? I do know that it wouldn't be the first time someone stuck a fancy name on an existing product and sold it for a substantial increase if that was what they are doing here.


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## Bugpac (Oct 28, 2012)

You can certainly tell the difference between sae 80/90 and marine lube, just smell the stuff is the first clue, then put a little on your finger and see what comes off easier. Tho I do agree, manufacturers brand bottles with there name and up charge.


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## Tim Murphy (Oct 28, 2012)

CaseyP said:


> I'm not understanding why you asked the question in the first place if your just gonna go and put the cheap stuff in anyway. Listen to what has been said. Its called marine grade for a reason, its not just some fancy label they put on it so they can charge more. Its more because it for a boat and has additives in it to keep damage from happening to your lower unit when it does leak.



Dear Casey,

Then why does Yamaha, a well known and well respected manufacturer of outboards, spec straight 90 weight for their gearcases? They say ABSOLUTELY NOTHING about using "Marine Grade."

They must be angling to sell a lot of replacement lower units, right?

My thinking is that if it's good enough for Yamaha it should probably work for the Evinrudes as well. The only other outboard I have ever owned was a Yamaha 40/28 jet and it had no lower unit only a jet pump which I properly maintained with a shot of grease after each use. It's now 18 years old and working for it's second owner without needing so much as a shim or an impeller refinish/replacement. 

Viscosity, Interval and Level are the only things that matter with oil and grease, and level only really matters because it is a potential indicator of a larger problem. Oil and grease cannot vanish, so if you're running low it's obviously leaking out somewhere and attention is required.

All three lower units on the outboards I own were drained and refilled with 90 weight. Blue stuff came out and brown stuff went in. I'll report back next year if I have no issues and I'll be honest and report back immediately if I have a failure.

I'm betting you'll hear nothing from me until next October.

Regards,

Tim Murphy


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## CaseyP (Oct 28, 2012)

Tim, I wasn't trying to prove a point or anything like that. I just didn't understand why you asked it if you were gonna go ahead and use the cheaper of the two. If it were my engine or lower unit, it would be getting marine oils.


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## Loggerhead Mike (Oct 29, 2012)

It would be easyer to argue brand vs brand than marine vs gl-4 or gl-5.

Tim will be fine


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## Charger25 (Oct 29, 2012)

Yeah Tim probably will be fine, but comparing lower units to jet drives is apple to oranges. Most gear boxes are vented to allow for expansion due to heat. Lower units however are submersed in water ,which dissipates the heat so they don't get hot if they are in good working order. What I was taught was that marine grade does not foam up as bad a automotive gear oil. But for me personally, its about piece of mind. If the manufacturer recommends marine grade the so be it. On new engines I'm guessing it would void the warranty if you didn't. 
One of the few times I've gone against it ,is in my CJ. AMC stated to use transmission fluid in the manual transmission and transfer case.
( T-5 & DANA 300 ) Reason being ,they have some bronze gears in them and newer lubricants will attack and corrode them. After much research, I use Valvoline syn. 75-80 which has better lubricity ,takes heat better and will not harm the bronze like GL-5 will.


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## Bugpac (Oct 29, 2012)

A bunch of new vehicles use atf instead of 80/90. In the gear box and the diff.


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## Andrew04 (Oct 30, 2012)

If even a drop of water is entering your lower unit, you'be got bigger problems. I use automotive differential oil 80-90 weight, and pressure test lower unit every season. No leaks means no need for mystery "marine" oil. Oil and water don't play well, and they don't lubricate or protect when mixed, regardless of fancy labeling. 

Spend the extra on new seals and gaskets. One drop of water is a failure.


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