[Creek Runner]

To be honest you can use regular 90wt from any auto parts store.
but it's like anything else you have a good, better, and best. Marine grade gear lubes are deigned to emulsify water and suspend it. Where as non marine LU oil isn't, so if you use something other than a marine grade I would recommend changing the LU oil frequently.

I use Mercury high performance gear oil in all my outboards, (except my F350 Yamaha) I also run it in my rear ends on my trucks. It's really good stuff!

 

[Creek Runner]

If you are referring to their Synthetic Blend High Viscosity 80W 90 yes you can run it in. Don't know if they make a full Synthetic LU oil.

Don't have much info on it as I don't use it, but its a marine grade gear case oil so you should be fine.

If you make the switch to the blend, buy some extra and once the LU has drained pump from the top with the bottom screw out to flush the non Synthetic blend out.

Then proceed to fill from the bottom like your suppose to!

 

[Creek Runner]

Hey rkmurphy also keep in mind that all your Quick silver products are the same as mercury which are sold at retailers like Wally world, Academy, West marine, etc etc!