Lower unit advice

[gomes512]

I completely forgot about this and have been meaning to ask this a while. When fall rolled around I had winterized my fathers boat since he hates working on cars/trucks/boats/etc..

I always used the factory fill of Sierra? lower unit oil. The stuff that is green. Unfortunately they did not have it in stock at the time and one of the guys told me I could just use a 80w-90 gear oil. I think I used some regular valvoline 80w-90 (can't remember if it was GL 5 or 4 will have to check sometime this weekend).

If it was a GL-5 can it be run safely in a mercruiser lower unit? Or should I replace it? Would a GL-4 be ok?

Thanks for any input

 

[Ryan02SS]

What type of drive? Alpha? Bravo?

If it's Alpha you can run a 80W-90 GL5 oil and probably be ok but automotive gear oils do not have the same ability to mix with water and still be able to lubricate and keep the gears alive. As cheap as the Merc or Sierra gear oil is, it's cheap insurance to change it before use.

For an Alpha you can get away with regular Merc or Sierra gear oil as the Alpha's use a Dog style clutch to change between F and R. If its a Bravo you have to use the Merc or Sierra Full Synthetic as it contains the friction modifier additives needed for the Bravo style cone clutch setup.

HTH

 

[Schmoe]

The High Performance stuff from Mercruiser is synthetic and green. I would not put a "regular" oil in the outdrive. Even though they are sealed, water will still get in there and you need an oil that can combat that. I used to use the High Performance stuff in my alpha, but really was overkill. Went with the dino version, can't recall the name, but it's brown and works well for Alpha's. I believe Mercruiser absoultely requires you to use the synthetic stuff if you have a Bravo drive, and as much as those costs, I for one would not hestitate using that oil. It ain't cheap, but it's good stuff. In fact, one of my very first posts was with the original BITOG owner and he conducted a homemade test comparing Amsoil and Mercruiser oils.

 

[gomes512]

Thanks for the replies!

I believe it is the Alpha drive I will in fact drain and refill with the Mercruiser stuff when the season starts again to be on the safe side.

Thanks again for the help.

 

[w9awx]

I would use the Mercury Synthetic. Two bottles are enough and it is cheap insurance. The only other option would be a synthetic 80/90 automotive gear oil.

 

[Volvohead]

For the one quart that an Alpha needs, I'd just use the Quicksilver HP lube. The price difference is peanuts next to a lower unit repair or even a fill of gas on the water.

 

[PT1]

Don't use automotive gear oil unless you change it several times a season. Water does intrude in all lower units and you will notice as you drain it it will be milky from the water. Marine grade lubes are able to withstand the mositure and protect the bearings in the lower unit effectively.

 

[Gillsy]

Originally Posted By: PT1
Don't use automotive gear oil unless you change it several times a season. Water does intrude in all lower units and you will notice as you drain it it will be milky from the water. Marine grade lubes are able to withstand the mositure and protect the bearings in the lower unit effectively.
I had water infiltration in all my Merc products (outboard, and i/o). My Johnson did not, and my current 07 Volvo SXA does not. I use Mobil 1 gear lube. It meets Volvo's spec. I have seen some marine stores (retail, and mail order) sell it as well.

 

[PT1]

Originally Posted By: Gillsy
Originally Posted By: PT1
Don't use automotive gear oil unless you change it several times a season. Water does intrude in all lower units and you will notice as you drain it it will be milky from the water. Marine grade lubes are able to withstand the mositure and protect the bearings in the lower unit effectively.
I had water infiltration in all my Merc products (outboard, and i/o). My Johnson did not, and my current 07 Volvo SXA does not. I use Mobil 1 gear lube. It meets Volvo's spec. I have seen some marine stores (retail, and mail order) sell it as well.


Yes, your units don't leak water yetbut once the seals do get a bit old you want marine grade lube in there to prevent toasting your bearings the first time a seal gets a bit worn. Water will intrude long before lubricant will leak out so the only detection is draining the lubricant and if you don't do it soon enough you will be spending quite a bit more than the cost of marine lube. Don't ask me how I know this...

 

[lars11]

If you "always" get a milky oil in the outdrive, you have a leak. Service it IMMEDIATELY! The oil should not be milky at all.
Even so, when theres a leak, the drive will be less damaged with a marine gear oil in there so that's what you should use.
Almost all drives have different requirements, ranging from the older Volvos that should have "the same as the engine" to clutch Alphas and outbords that use 80w90 or straight 90 mineral/semi synth GL4 or GL5 to the dual prop drives that requires VERY specific full synth 75w90 oils.
But again: Milky oil = damaged seals or crooked/scored axles.

 

[Volvohead]

I agree with lars11. Once any milkiness is detected, it's time to reseal the outdrive, pronto. A lubricant's ability to put up with water is not a substitute for effective seals and gaskets.

However, most boaters (unless they trailer and/or run a lot of hours) only change out outdrive lube once a season. So if it starts letting in water, it may not be discovered right away. A lubricant with superior water dilution characteristics gives some added insurance.

IIRC, besides the Quicksilver HP, Amsoil's marine lube has good water dilution characteristics. Other than those two, I'd be cautious about running a typical automotive grade gear lube in an outdrive continuously submerged in water.

 

[FZ1]

I run Evinrude /Johnson Ultra HPF. Change it every Nonember. I come out looking just like it went in.