Here is my take on what is the best drive oil:

Mobil-1...users like it..easilly available...PAO

Amsoil...New formulation...PAO...Good company

Royal Purple...not PAO but repels water best

Torco...PAO...Mercury uses it the #6's....wow

Redline....75W-140 thick and may foam due to air trapping
use 75W-90 in my humble opinion.

Alisyn....PAO...good formulation...loyal users

Mercury HP....Semi-synthetic limitations but very good

...and the winner is...the one you pick!

I've been running royal purple max gear 75/90 in my bravo for two years with out any problems and little to no metal on the magnet.
Good stuff.

Yup it's all Martin Marine uses and they love it I hear.

I ran the green merc fluid in my XR drives and it was fine. I changed over to the Shockproof Redline and picked up a mile per hour and the drives shifted much smoother. I was very happy with the results and especially the easier shifting.

Anyone else that are using the Merc Hi-Per oil also get the 'sludge' buildup in your drive bottle? I have completely drained mine 3x in the 2 yrs I've owned the boat, R&R the bottle to clean it out too, and it still has this sludge each time. Last spring was both drives rebuild, so all was perfectly clean to start with, yet last week when I drained to change, it had this again. I would think it's gotta plug the hose. Has to be something with the Merc lube as a friend gets the same thing. What's the deal?

Jerry,
Have you thought about analyzing the sludge to see exactly what it consists of? I used to have a small amount in my old B1 but none since I swapped to an XZ. From what I remember it appeared to be an aluminum paste.

What do you all think about the 75w90 in a heavily loaded Alpha? I went to the above link but can't find the products......

BH

Merc HP in an Alpha is fine they recommend it as a matter of fact since 1981 with any 350 Mag engine set-up.

US1, Every season I've used the Merc oil, I've had to clean the sludge out of the bottle when I've change the drive oil for the next year. It took 3 changes with Amsoil to get it out before I had the drive rebuilt. The drive had 550 hrs. on it. I had noticed that there seemed to be more sludge in the bottle each season, before putting the drive shower on.

Mercury HP can leave that residue you are talking about...it may just be a settling out of a suspension of the additives..

But the stuff works and it works pretty good.

In my new boat it's going to probably be Torco since it will have #6's and that's what Merc is using. I called down to Reggieland and they do have cases of Torco "laying around"...I was told