What type of fluid would be best for this transmission?

I've always read and been told Type-F. It is for constant heavy loads.

Thanks Rookie thought so, but wasn't sure!

From the Velvet-Drive Manual pages 6-7. People recommend Type-F because of it's higher coefficient of friction under loads. (grippier)
https://www.boatdesign.net/attachmen...ual-pdf.81273/
"Type of Oil. Dexron, Type F, or any hydraulic fluid which meets the C-3 oil specification is acceptable. Do not mix different brands. If engine doesn't exceed 3,000 R.P.M., a premium grade 30 weight engine oil is acceptable. SAE #40 and multiviscosity oils are not recommended. If the transmission oil temperature has exceeded 190 0 F or the alarm sounds, the oil must be changed in the transmission and cooler system. Changing Oil. Oil in transmission, cooler, and cooler lines should be changed after every 1,000 hours of operation or annually. Severe service conditions or high operating temperatures may require more frequent changes."

Im rigging right now and had to drain the oil in my bam 1350’s (new to me). Oil looked great but as long as I had to drain for plumbing etc purposes should I use the same? Type F.

I only use Type-F in my 71-C Scarab transmissions. That's what my re-builder said to use and would be good to 700HP. I developed a crack in one of my coolers and water was getting in there and foaming. Valako and were running from Muskegon back to GH dumping 1/2 quart Type-F every 3 miles into the transmission to get back. Don't know if the fluid is what got us back or not. I've just stuck with it since then.

Non-synthetic Type F is the one to use. We did actual testing with a number of fluids and there is a 14% spread in break away torque between them with F having the highest,