black smelly gear lube

[Tucker]

Ok, bringing this to the top cause I don't savy.
Yamaha says don't use GL-5 gear oil in a LU with bushings. So it looks like the Bolt is implying that GL-4 be used in a LU with bushings right? And now we have oils that are GL-4 & GL-5 compatitble. WTF? I've been really screwing up. I use Mobile 1 90W gear oil and don't know what GL it is. I need to get this right, does that mean spending $16/quart for the OEM stuff? LU gear oil change just went up to over $50...wonderful. I think to use any kind of comparison between auto lubs and outboard lubs in this application is unwise. There aint anything spinning 5500 RPM in any auto tranny.

[rodbolt17]

in the owners manual it says use yamahalube, it also gives the specs for the actual engineers callout.
the PROPER lubrimatic,or other brand, GL-4 oil found at napa or wally world will be just fine.
hypoid spiral bevel cut gears,bevel cut gears and spur cut gears are simply that.
the biggest difference is in how the rotating asymblies are made.
gearcase lubricants,unlike auto trannys, need to have additional additives for water dispersion.

[seahorse5]

For those who want to learn more about gear lubes, here is a link to a test of various ones both with and without water. It's been posted on several websites over the years but it is still a great reference. The graphs are very small but are full size in the magazine.

Watered Down: How Gear Lubes Perform With Water Added