The spec for my Honda 135 outboard gear case oil is: API STANDARD( GL-4/5) SAE 90 outboard motor gear oil.Does this mean that I can use GL-4? I have a lot of GL-4.
I have used Amsoil products for 15 years and love them. I'm sure the marine gear oil they have is great, but I have not had a chance to give it a real world test.
I have a 60HP Merc I will be trying it out in the summer though.
I'm positive it's a much better product than the Honda stuff that is a dino gear oil. I have seen some guys with commercial boats coming into our shop that have some pretty dark Honda gear lube coming out after some hours on it. I don't know how many hours they put on though.
I work at a Honda marine dealer. Honda gear lube is a partial synthetic gear lube. So You might want to either use the honda gear lube or move up to a Full Synthetic gear lube. If you run a dino gear oil change it often or keep a close eye on it.
Some of the boats that come in beat the snot out of the Honda partial syn gear lube. They run it out too far.