Marine Gear Oil for lower units

Do you really think automotive gear oil will trash your $6000 lower unit? As in, its Ok for a lamborgini rear end, but not my boat lower unit
There are also known issues of "slippery" non VP lube causing slipping/damage issues with the cone clutch in the VP. Merc uses dog clutches....VP does not. And its great lambo works great with that..... but how many lambos run at 3/4 throttle or more for hrs on end like a boat does when up on plane? Boats are biiiiiggg $$$$ to repair, and I sure wouldnt be trying to save $20 on lube you change once a year.
 
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At the end of the season, I remove the lower plug and let any accumulated water dribble out along with a bit of lube. I then quickly clean the magnetic plug, put it back in and leave it for the winter. In the spring I drain it completely and put in fresh lube. Here is the paper towel showing a bit of water, some lube and the reside from the magnet. It’s a 27 year old Yamaha two stoke. Maybe I’ll change the seals, maybe not. :D

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Today I bled the rest of the lube, using paper towels to help see if there was any more water left. Nope, just pure lube. I drained the rest of it and then pumped in fresh 90 grade Motomaster Formula 1 marine lube. I used a pump hose with a conversion to Yamahas.

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There are also known issues of "slippery" non VP lube causing slipping/damage issues with the cone clutch in the VP. Merc uses dog clutches....VP does not. And its great lambo works great with that..... but how many lambos run at 3/4 throttle or more for hrs on end like a boat does when up on plane? Boats are biiiiiggg $$$$ to repair, and I sure wouldnt be trying to save $20 on lube you change once a year.
Merc uses cone clutches in the Bravo 1, Bravo 2 and Bravo 3 drives. The Alpha uses dog clutches. Not sure about the older TR and TRS drives but I assume dog clutches. (The Alpha is for smaller engines up to about 300 hp, Bravo is for more powerful engines).
 
I know mystic is well regarded for other applications on this forum. Any thoughts on the mystic jt4 marine out drive gear oil? Not much more than plain old 80w90 at Oreilly’s.
 
WalMart sells Mercury/Quicksilver gear oil. Try there.
Used it in 3 brands of outboard motors … BiL used nothing but in his I/O (MC 4.3L) …
Always held up well - and yes, have had seal leaks until repaired …
 
Well if that's true, then there is a pretty good reason to never buy Quicksilver's marine gear oil. Any formulator making a marine gear oil who isn't formulating for water emulsibility is either; negligent, ignorant, or just a plain ole' meanie......probably hates puppies too 🐶
Had read somewhere about emulsion protection - but also tackifiers and anti-corrosion packs being different too …
Can’t imagine with the loads/speeds Mercs put into the lower units - plus the operating environment - that they play decal games with OTR oil … Folks should get a bottle of the Merc HP 90 and see if they think that’s SuperTech.
I find one company guy who says something controversial seldom represents what R&D teams bring us …
 
Outdrive gear oil is an example of where you use a small amount per year (QT or two) and the difference between OEM gear oil (at Walmart) and other brand names of outdrive gear oil or even Supertech is a few dollars or less. I think it only makes sense to get the OEM at Walmart.
 
I always use Mercruiser high performance gear lube. It takes 2 quarts and it gets changed once a year. You can get it at Walmart. Replacement outdrives are thousands.

$20 a year for gear lube. Why scrimp to save a few dollars?
Well some boats are used so little that the lube could easily last 2 or 3 years. I used to drain it into a clean container in the fall. If there was no water, which there never was, I would reuse it. No sense tossing perfectly good gear lube.
 
I've historically used penzoil marine gear lube with good success. I had an old outboard with a badly leaking foot and it did a good job keeping the water in suspension. I've got some supertech for my next change just because that's what walmart had.
 
I always use whatever automotive gear oil I have on the shelf. Last year was 85w140 and this year is 75w90 (I think) and have never had a lower unit failure. I purchase the least expensive gear oil I can find.
 
This is my first Volvo Drive ever and I have been boating for ummm ... over 4 decades.
Owners manual specs Volvo Gear Lube of Mobile Delvac Synthetic 75/90 for the SX drive.

Im partial to Mecruiser ONLY because I know them so well, with that said, the Volvo SX, wow, very impressed so far, for the most part. Either way, to me outdrives are a PITA as time goes on and they age.
In 2007 I bought a Stringray 195 LX with a Volvo Penta SX drive system. I thought it was superior to the Mercruiser. The cone clutch was quiet, and I never saw any particulate, or milk in the lube that I saw with Mercruiser. That being said, Volvo Penta service is not available locally for me. My manual also called out Mobil 1 Delvac 75w-90.
 
Given that you only use 2 or so QTs of gear oil, why not use the manufacturers lube if available?
do you think they use the best ingredients possible or just for the marine additive pack?
Of course gl-4 or gl-5 is important as well as what is actually recommended.

If in doubt the oem product is always a good choice.

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Given that you only use 2 or so QTs of gear oil, why not use the manufacturers lube if available?
Volvo Penta owners manual states Mobil 1 Delvac 75/90 or VP gear oil in their SX-A drives.
Best price here but I see this year is a special order, Worth the effort to me and glad that I saw this post because I better get ordering🙃

 
Slightly OT: anyone know a good source for drain/fill washers in bulk? Aren’t you supposed to use a new washer every time you remove the plugs?
 
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