I am in process of changing my outdrive gear oil on my XR upper and IMCO lower, Amsoil or Mercury Marine both offer synthetics any thoughts or experiencers?

Nothing but Amsoil in everything I own-motor oil, gear, etc. My mechanic took apart my drives last year and couldn't believe how clean the oil was and how great (no wear) they looked. Bravo ones behind HP500's on a 32 Fountain.

Amsoil also every 20 hours 60 hours still spotless when changed, I run it hard with pair of 650s XRs
Rich

Are you running this version?

AMSOIL AMSOIL Synthetic Marine Gear Lube 75W-90

Mercury Hi Performance gear oil. 460+ hrs and still counting. Still comes out like new.

You should use Severe Gear if going the Amsoil route.

Yes. I have used this in multiple performance boats and have great results. Never needed the severe gear oil. I don't know if it makes a difference but it is not listed as marine and don't know what makes "marine" but marine version has worked well for me.

I did some research way back when, but I believe the Marine Gear Lube is standard marine gear lube. Not "high performance". You should read up on it before making your choice. I ran Severe Gear in my XRs behind 575's in previous boat.

The standard, everyday Merc gear lube is "High Performance", the correct gear lube for XR, #6s, etc is "Extreme Performance". As of 2 years ago Quicksilver Extreme Performance and Mercury Race Gear Lube are the same oils, just different packaging. Also, as of 2 years ago the Extreme and Race are brown in color, not blue like in the past.

George at AADS said he moved away from Severe Gear Amsoil as they did something to the formula that was causing cone clutch failures. No such issue with marine Amsoil.: