I'm using AMS 75-140 severe. The oil in the bottom has no chance to circulate. Running fast all the time is taking its toll. Thanks for the suggestions..any others. I think I am going to start changing every trip..10-15 hrs.

Yeah, but most dealers won't stock it....A friend has a small repair shop and they order the 5 gallon jugs for themselves. I asked them to order one for me too.

see.....

I modified a lawn/garden sprayer to automatically pump the fluid up the drive. It works great. I have XZs and also use the Mercury HP stuff.

I use the Amsoil Marine Gear Lube and change every 25hrs.

I think thats for outboards... I found that to & took it back... you need the gear lube with the "+" on the label
Im sure it will work but its not the good stuff...

Specifics on modifications please?

this is what i use... not sure if its the same hp as you have... may want to ck.