Classic Australian Wooden Power Boat Association

What oil do they use in the box

Gear oil,

And if you'd like a slightly more detailed answer ……..
If it's a H&H Z drive, 400ml of EP80/90
Source … Philip Haynes.
BobW

Thanks guys
I will fill it tomorrow

Some of the racing hydro guys run transmission oil. They reckon the boxes spin with less resistance there for less load on the engine.

Bootlegger

I would have thought that less resistance inside the gearbox equals more power to the prop. I have had that discussion with Graham Howard.

Bob