I can respect that and my bad for letting my temper take over. I thought initially you were indeed insinuating that I view myself as an expert, which now I see, that wasn't your intention at all. Classic miscommunication! It's all good.

I ran the neo oil from The Bravo Shop in my HTM with 1200 hp and a B-Max with great results

Borgie play nice:riding:

This weekend I changed out the oil that Collabella put in there last year and it came out really watery , poured right out .

The oil that going back in (Mantek 80w-90) is thick and has a consistency of honey, it wants to stick to everything. It took 40 minutes to fill one drive with my Menards special set up. (thick) I like it. I believe Colabella fills em with Mercury oil .. it was green/blue in color

http://33outlaw.zenfolio.com/img/s4/...61732489-3.jpg

Update. Logged over 400 hard miles on the boat since I switched to the Mystik 85w140 lube. No more metal on the drain plugs. Also, I didnt lose any top speed. I like the tackiness of it. Also like the red color of it :). Very happy with it for 65 bucks for a 5 gallon bucket at farm and fleet.

I posted before that Mystic oils were made by Citgo and I have had good luck with them as well for the past 2 years in boat apps that I have serviced. Also Merc premium blend gear oil is made by Citgo.


Mystic has very good 2 stroke oil for outboards and another one for PWC's. FWIW.

Was just reading a test where they had a 26ft cat, bravo drive, 600HP engine. At 5400RPM, drive oil temps were recorded 352*.

The other test was a 24ft deck boat, with a 330HP 454. Max oil temp on that was 239* at 4400RPM. Obviously less power, and less rpm netted a cooler running drive. And also, would probably live 1000 hours behind that combo


352*, imo, is PHUCKING HOT!!! I certainly wouldn't want my engine oil there.

I am certainly no oil chemist, but, I'd like to think, that the majority of gear oils, are not designed to be used in that temperature range, nor are their viscosity ratings measured there. I'd surely like to know, what the viscosity of a 90 weight gear oil is at 350 degrees, and what a 140 weight oil is at 350 degrees.

I have had people tell me I am silly for running 75w140 lube in my drives. IDK, maybe I am. Mercury specs 75w90 in their drives. Good for them. Their drives also break all the time, especially when pushed to their limits.

My theory, is do what you can to keep the oil cool, and if the temps are extreme, look into a heavier viscosity, along with a good synthetic oil. Doing that, just may help keep them gears from pitting so soon. I know if my trucks rear axle regularly got to 350+ degrees, or my transmission, I certainly wouldnt expect long life from them either.

The correct viscosity must be selected independently of any specific gear stage, realizing that a compromise is required for multistage gears. The selection of the correct viscosity is based on the oil’s expected operating temperature, such as sump temperature or the temperature of the injected oil. This temperature is calculated by determining the gear’s thermal economy, taking into account the frictional losses; or in the case of gears already installed, by measuring the temperature of the sump. It might be required to select a lower viscosity to ensure lubricant is supplied during a cold start or at lower ambient temperatures. In each individual case, it is necessary to check the viscosity at the existing starting temperature, especially in the case of oil circulation systems.

A typical worksheet method for determining the viscosity required for a spur gear drive and a worm gear drive starts with the calculation of the force-speed factor. Because of different viscosity-temperature (VI) behavior of different oils, different ISO viscosity grades are selected for the same Kluber Viscosity Number.

Played around with some engineering stuff. :bigbird:

Lets take a look at the viscosity levels, of a 75w90 lube.

At 212* F a 90 Weight will have a cSt of 13.5. At 350 degrees, the cSt drops to 4.31.

Lets now look at a 75w140 weight lube.

At 212* F, a 140 weight, will have a cSt of 24. At 350 degrees, the cSt drops to 10.15. (so, the cSt is actually lower with the 140 at 350*, than the 90 at 212*)

So, what you can see here, is even though you have 140 oil, if the temperatures are high enough, you actually will have less viscosity, as you would with a cooler running 90 weight oil. If you are running a 90 weight oil, at those temperatures, obviously you can see just how the viscosity drops down to a very low number of 4.31. Think of this, a 10 Weight engine oil, has a cSt of 4.1 at 212*F!!!!! You guys would freak out running straight 10 weight oil in your engines at 6000RPM, with 75psi of pressure helping it out. But, in a gearbox, with splash lubrication, getting pounded on, direct metal to metal helical gears, "its just fine''.

We all know a stock bravo with 400hp will live a long time. We all know our cars differentials last a long time, with say a 75w90 lube, and its viscosity level. Its almost like a known successful working scenerio. If my differential has lasted 150k miles, with an average operating temp of say, 175 degrees, and xxx viscosity, I'm fine with that right? Now, my boat drives? I cant do a whole lot to control the temp of the oil in them. All I can do, is aim for a known working viscosity, as far as temps go. If my 90 weight gear lube had a cSt of 13.5 in my differential, or low HP sterndrive at 212*, I'd like to maintain that cSt, with my new found higher oil temps. To do that, the only thing I can do, is switch oil weight, or reduce temperature.

I certainly don't expect my gears, to have the same level of protection, with a higher load on them, higher RPM level, and higher operating temps, while still using the same lubricant.

I do not see the downside to a more viscous oil, in a gear box, other than some extra drag. Now, where pressurized flow is a concern, like say a dry sump, that may be another story. If Chrysler seems to think factory fill for my 2008 Grand Cherokee's front and rear diff's of 75w140 is good, I'd think its good for my sterndrive that's seeing tremendously more load. 180k miles so far on my Jeep, so far so good. Now, I'm no scientist, so this entire post could be one big pile of chit information lol.

I've heard really good stuff about this oil. I am running it next oil change too.

been using in customer boats for over 2 years not a problem but will add most are under 500 hp.

The new Mercury HP gear case oil is "Mercury Racing Gear Oil", part number 92-8M0078016 for 5 gallons. The O/B 300 XS guys are using it. They are terribly hard on gear cases!