Marine-grade Transmission Oil

[Tmac897]

Hi,

I live on the water in New Jersey, and I have a boat. I noticed that the gear oil for my lower unit, I.e. the transmission, is SAE 90 and GL4. Seems to be the exact specification called for in the shop manual for an Elan transmission.

Reading various posts/threads on the subject here, it seems like many people are trying to get something close to that spec with various products. Most of what I’ve seen in the Autozones and such are multi-viscosity, multi spec (GL4 and/or GL5). I’m certainly not an oil expert by any stretch, so I’m just posting this on the off chance it might be helpful.

The product I use in the boat is Mercury Quicksilver Gear Oil, SAE 90. It’s readily available in any marine supply store, or mail order from West Marine, Overtons, or even Amazon.

I’m still in the restoration phase, so I haven’t tried this in my car yet. I know there are a few really oil-knowledgeable members here.

Any thoughts?

Best regards,
Tony

[h20hamelan]

is the GL5 going to eat the brass?

[Tmac897]

is the GL5 going to eat the brass?

The Internet says:

Most modern GL-5 oils have buffered additive packages that will not corrode or directly hurt soft metals. HOWEVER: When used in transmissions with brass synchronizers they will cause higher temperatures and higher wear on those parts.

[USA64]

I think what he's saying is that one can get 90 weight GL4 at a marine store.

[Tmac897]

I think what he's saying is that one can get 90 weight GL4 at a marine store.

Well, yes. But also asking if anyone sees a problem with using marine rather than automotive products. And even, is there an advantage in keeping to the original spec, or have modern products surpassed the capabilities of things we used when The Beatles were the new kids on the block?

[Andy8421]

Well, yes. But also asking if anyone sees a problem with using marine rather than automotive products.

In my experience marine products bought from a chandler are at least twice the price of the equivalent product in an auto store.

[Tmac897]

Well, yes. But also asking if anyone sees a problem with using marine rather than automotive products.

In my experience marine products bought from a chandler are at least twice the price of the equivalent product in an auto store.

That’s true of many things marine. In this case, it’s pretty comparable to automotive products. Cheaper than Mobil 1, for example. About the same as some other brands. I’m going by Amazon prices right now.

[jk952]

Not an expert by any means, but some (differential) gear oil products have molybdenum in them, not good in a transmission. Marine drives don’t need syncros so what may be in it? Sold my boat years ago..
I would make sure any product is specific for use in manual transmissions.