Whats the best lower unit gear oil?

[hydro13]

Want to change the lower unit gear lube on my 2.5 260 HP with sports master lower unit....
What is the best lube to put in it? How much goes in it?


Thanks for the input

[D.B.S]

Merc Hi performance

[Ted Stryker]

Merc Hi performance

Yep, and fill it from the carrier until it start to flow from the top hole then some will flow back out from the fill hole as You try to get the plug back in and that's about enough... I can't remember the ounces, but I'm thinking it will actually hold about 28 oz. but is designed to operate with about 24(ish) oz... I may be wrong, but that's what is coming to mind...

[mcyama]

Tried and True 85-140 petro base when it comes to durability. Thanks Martin

[flabum1017]

Tried and True 85-140 petro base when it comes to durability. Thanks Martin

get a little water in it and the bearings are done, with the merc stuff, there is a good chance nothing will be damaged.......

[Ted Stryker]

The 85-140 won't hurt anything, I've used it to top of in a pinch but the Merc 90 weight is more suited for this application, so sayeth the engineers and chemist that are smarter than most... Oil viscosity is a function of operating temperature, and in this case You will almost certainly be better served with 90 weight...

[h2oskiier30]

22.5 oz for a sportmaster...according to the Merc manual.

[Markus]

I would use a full synthetic marine gear lube such as the Pennzoil product. It will not be quite as good at dispersing water as the Merc stuff is, but it will provide much better lubrication.

[sho305]

I've experimented a little with lube in far less powerful motors. In my old I/O that takes a gallon I ran 140 and then went to 90, gained some speed for sure. In my little 85hp I ran normal 90 marine lube then synthetic lube, gained 1-2mph. Then I got some straight 40 motor oil and put about 20% in with the synthetic and gained another half mph or so hard to tell. Since that was an 85 and they use the same LU for the 140hp I figured it was low stress and I could get away with it, didn't put many hours on it either. Of course with a more expensive and high performance outboard than a force I would only use highly recommended lube or synthetic. The same rated synthetic is typically not quite as thick, I am pretty sure that is one reason it makes more power and why I tried mixing even lighter oil in just to see. Of course LU gears are very high stress so not a good idea with big HP. Back when we ran Bravo outdrives we ran only Merc lube, and we changed it very often like a month of weekends often. We had no problems with 500hp built 454s we ran for years on them.

[Euro Muscle]

I always run (100% Synthetic) KLOTS SAE 90 gear lube in all my boats its good stuff.:thumbsup: my 2 cents

[Scott in MN]

I always run (100% Synthetic) KLOTS SAE 90 gear lube in all my boats its good stuff.:thumbsup: my 2 cents

I ran the Klotz stuff for one month with a leaking CLE. Everytime out I would change lube and drain a pink milkshake out of the lower unit but it held together so I would say the Klotz is good. Now I run the Merc high perf. but would use the Klotz no problem.

[Cp]

Merc Hi-Perf is the ONLY way to go. With it, a little water intrusion does NOT toast the gears. I don't think even Klotz will perform like that. It's always less painful (wallet) to replace a busted seal than all the hard parts too. I've been there and experienced it, both ways.

Oh, and with the Sporty, you need to let a bunch of it drain out before putting in the carrier seal. Other wise it will either push through the shift shaft seal, or blow the prop shaft seal.

[Jay Smith]

Merc High Performance in a recreational L.U. is hard to beat.

If I were drag racing trying to extract every ounce from a combo I'd run the Alyson 0 weight.. I have even used ATF at a race but changed to Merc oil while testing...


My .02
Jay

[sho305]

Merc High Performance in a recreational L.U. is hard to beat.

If I were drag racing trying to extract every ounce from a combo I'd run the Alyson 0 weight.. I have even used ATF at a race but changed to Merc oil while testing...


My .02
Jay
While racing sure lol. I bought a little turbo car once and after a couple months got tired of the notchy shifting, bought some synthetic lube. I went to drain it and I thought it was full of water at first, must have been pure clear mineral oil. Shifted much better after that. Likely some stupid kid saw that trick on the internet or something, it was not a race car and he could have bumped up the boost for way more improvement like I did.

[Ron V]

Bel Ray #413 is comparable to Merc Hi Perf and I've been running it for several years. Smells the same, looks the same, seems to protect the same.

Something that is being forgotten is that while lower unit gears are relatively small for the amount of power being run through them, the lower unit is also cooled by water constantly, unlike an automotive differential. The lake is also a huge shock absorber. I know guys who run the same oil (automotive hypoid, no less) for multiple seasons and it looks fine, never give it a second thought. But in something like a 2.5 it is very, very cheap insurance to change often and run the good stuff.

[seahorse]

For some gear oil test results, this article has been around a while.

http://bwbmag.com/output.cfm?id=1891729&sectionid=308

[Markus]

For some gear oil test results, this article has been around a while.

http://bwbmag.com/output.cfm?id=1891729&sectionid=308

That article is beyond dumb. Mr Grannis gets some random tests done, including one where Wal Mart oil mixed with water performs the best. The oils are all over the place in the tests. Then he declares Evinrude's oil the winner. By the way, he is an Evinrude service manager... :rolleyes::rolleyes:

[stokernick]

22.5 oz for a sportmaster...according to the Merc manual.

overfill and you could blow out the seals.

[Bruster]

I gotta ask, how can you over fill a lower unit?

[stokernick]

something to do with the expansion of the oil when it gets hot,don't know haven't had the problem!

[Bruster]

No, I want to know how, not why.

[Euro Muscle]

overfill and you could blow out the seals.

I always fill to vent hole and drain back 2oz , for expansion. its a good idea, never had seal problem.a little less is better than a little more.......My2cents:D

[Bruster]

Must be the engineers who design these high performance gear cases don't know anything about heat, oil expansion or lubrication. If they did they would have put the vent hole a little lower (2 oz lower?) in the case. Ya think???
If you are really worried about oil expansion run a vent kit, anything less than full is just asking for trouble at some point in time..


I always fill to vent hole and drain back 2oz , for expansion. its a good idea, never had seal problem.a little less is better than a little more.......My2cents:D

[Capt.Insane-o]

One of the best features of Merc Hi Perf is it's very low expansion characteristics along with an exceptional ability to disperse water contamination. Plus it's on the shelf just about everywhere including Wal-Mart.

[Bruster]

Capt'
You home all ready? Did you burn all of that tank of fuel today? Great weather. 'eh?

[Capt.Insane-o]

No... I had to work all day deep in a hole of a Chris Craft that I'm sure dated back before Noah's Ark. I did get to play around on the Saginaw Ditch, and yep, tank is empty. :D I'll call you in the morning.

[stokernick]

No, I want to know how, not why.

I disconnect the fill hole before I put the vent screw in,simple physics!

[sho305]

I never had a problem with an OB filling it to the vent every time. However, with my ancient eaton outdrive on the ChrisCraft it pukes the lube into the boat when you run it for a while, and the LU does get warm for sure. I put all new seals in there too. Will build a vent system for it if I ever have time to restore the old hog. Everyone loved that old V8 though, too bad they didn't know enough how to build stringers in a FG hull back then.

[Ron V]

As far as blowing seals, yes it can happen. The propshaft seal on my dad's '71 Merc 650 popped halfway out after sitting for a winter. We've also had oil force its way past the upper driveshaft seal and out the water weep hole. The answer? Make sure the lube is kept at a warmer temperature than the motor prior to filling. In the summer, keep the oil in the hot garage instead of in a cool basement. In the late fall, keep the lube in the house where it is warmer than the motor. That way when you are winterizing the boat, you're not putting 32 degree oil into a motor that will see triple digit temps come summer. This helps with the expansion problems.

[Bruster]

overfill and you could blow out the seals.


I gotta ask, how can you over fill a lower unit?


something to do with the expansion of the oil when it gets hot,don't know haven't had the problem!


No, I want to know how, not why.


I disconnect the fill hole before I put the vent screw in,simple physics!

I think I understand the "physics" when you under fill it, what I guess I don't understand is how you can overfill a lower unit.

[Riverratt]

I think I understand the "physics" when you under fill it, what I guess I don't understand is how you can overfill a lower unit.

Give it an extra pump or 2 to compensate for the anticiapated lube loss when you remove the pump, install top screw and don't end up losing any oil when you remove the pump. There you have it the gearcase is over full.

[Bruster]

No it's just full, providing you have allowed the lube time to fill the small air voids and disperse all the air in the case (in which case it could be less than full). It is impossible to overfill the case. If you install the vent plug when the lube starts coming out the vent and give it a couple pumps you have pressurized the case. As soon as you remove the fill fitting to install the drain plug, any amount of pressure you have developed is released pushing any "extra" lube back out. You're just not that quick. The guys who build lower units for a living will tell you the same thing I have been saying.


Give it an extra pump or 2 to compensate for the anticiapated lube loss when you remove the pump, install top screw and don't end up losing any oil when you remove the pump. There you have it the gearcase is over full.

[RB in NM]

60/40 % mixture of mule piss and snake oil..........

No matter who you'll ask, you'll always get various answers, some of the replies will have some sort of biased history as to what the individual may have been running for the past forever with success. Others may have some sort of documentation / data about the oil they choose to run. Then there's those whose brother, cousin's mother on their sister's side heard someone used some kind'a stuff that worked purdy good.....

Gear Oil and other Lubricant discussions bring out the very best of the worst arguments you'll find in the boating industry. :)

The best rule of thumb I have embraced, is change it often, you'll find any issues early by doing so.

Ohh,,, any snake oil will work jus' fine,,, just use the good stuff. !

RB

[John Richied]

60/40 % mixture of mule piss and snake oil..........
RB :thumbsup:

Is that on e-bay or where do I order it from? :D

[Cp]

The shift shaft leaking issue is a Sportmaster idiosyncrasy. Full is too much. You will push it out the shift shaft seal if you're lucky, or push out the prop shaft seals if you're not. A known problem. Bruster, do you even have a Sporty?

[Bruster]

Shift shaft seal is a Mercury problem if you look a little closer. I'm just stating some facts. What's your agenda?


The shift shaft leaking issue is a Sportmaster idiosyncrasy. Full is too much. You will push it out the shift shaft seal if you're lucky, or push out the prop shaft seals if you're not. A known problem. Bruster, do you even have a Sporty?

[Cp]

So what's your solution?

[Burke Kilgour]

On a side note, I remember someone plumbing in a line to a container like the IO's use. Does anyone remember the details? I was thinking of doing this with my Sporty..................

[Dave Strong]

On a side note, I remember someone plumbing in a line to a container like the IO's use. Does anyone remember the details? I was thinking of doing this with my Sporty..................

I think Lakeland Marine in Havasu used to sell a kit.


Dave

[powerabout]

the shift shaft seal is the pressure relief valve on a Merc

[specboatops]

Last few seasons I've used the Alyson Full Syn Less than Zero weight stuff and have had no issues.......I also use to run it in mt Inline 6 xs Gearcase with great success.

Chris

[RB in NM]

The oil reservoir kit has been discussed on here before, maybe a search will bring it up. I have never had any issues on any of my sportys, least with oil seals leaking. I fill mine the same way I always have, till oil comes out the top vent hole, with fill hose still in the fill hole put in vent plug, then remove fill hose from bottom hole, let a little drain, plug the bottom hole and go have fun.

I have run all sorts of gear oils. The suggested Mercury oil meets all of Mercs specifications and fulfills their warranty requirements. You can not go wrong with what Mercury recommends, period. The other lubes out there have all sort of mystique surrounding them. What works fine for one guy, gets a bad rap from the next guy. One report will typically have some sort of initiative behind it's findings. I have narrowed my gear oil purchases to either Merc and/or Alyson. Both with great success and no issues to date.

[sho305]

Last few seasons I've used the Alyson Full Syn Less than Zero weight stuff and have had no issues.......I also use to run it in mt Inline 6 xs Gearcase with great success.

Chris

Is this the snake oil? I don't know anyone with mules around here but a guy does have some horses would that be the same....? :D

I am very convinced that changing the lube often on the Bravo I/O cases helped keep them from having problems when running a lot of power through them. Sure if you hit a wave with the power on you might chew it up with the impact, but other people had problems who left the lube in all year and were running over stock HP 454s. I'll guess that this is one of the best places to find out what lubes other than Mercury are good.

[RB in NM]

Is this the snake oil? I don't know anyone with mules around here but a guy does have some horses would that be the same....? :D

Nope, the PH levels are different ? ? mules are less Acidic , but smells stronger, a good odor indication for smellin' tha' leeks...:)

I used the Alyson zero weight in a 2:1 geared 200 case one season on my alli drag. I was a little more than suspicious about the zero weight, it came out super clean after 30-40 passes. I then used it the rest of the season without issue. As light as the zero weight is, the lower shifted in gear at idle much better than any other oil I tried, which seemed odd to me at first.

[Mrzip]

Klotz alway's worked for me...

[specboatops]

Nope, the PH levels are different ? ? mules are less Acidic , but smells stronger, a good odor indication for smellin' tha' leeks...:)

I used the Alyson zero weight in a 2:1 geared 200 case one season on my alli drag. I was a little more than suspicious about the zero weight, it came out super clean after 30-40 passes. I then used it the rest of the season without issue. As light as the zero weight is, the lower shifted in gear at idle much better than any other oil I tried, which seemed odd to me at first.

I agree on the shifting as well....I never had a hint of trouble....came down to cost and availability for me.......

[astro@ptd.net]

I winterized my 1996 225 ProMax yesterday and the last thing I did was drain the sportmaster. I was not very pleased to see a pukey lookin grayish fluid drip out of the vent hole first then out of the fill hole in the carrier. WTF!!! Since I didn't fill it I have no idea how much was put in and measuring what came out was useless as well cuz it was mixed with water. I just put the motor in service in April. Once I have it checked out and seals replaced I'll fill it myself with Alisyn Progear 21 Zero weight for next season. After ten hours of operation I'll drain, check it and then refill it for the remainder of the season.

I have read all I could find on water intrusion on 2.5L & 3L sportmasters and everything points to overfilling causing the oil to push out from heating up the oil and expanding so much that it pushes out of the shift shaft seal (or other seals if weaker)then cooling and drawing in water. I live in an area where the lakes are not big enough to make runs longer than a couple of miles at a time. Heck it wasn't il I went to the rally in TN that I made a run longer than 3 miles at a time.
s my guess is that the overfill/heat/expansion/cooling/draw in water is the culprit.

No matter what the reason, I'm PISSED!! LOL!!

[gmacrae]

If the merc stuff is the best at absorbing water, that's a good enough reason for me to use it