"TOG@Toil" wrote

Which was what I was thinking. I mean, what was max revs for a Merlin?

Googles

Hm. About 3000rpm. Just off tickover for a 'Busa.

But all the high power Merlins and such had gear reducing for their props.
They had to, to keep tip speed down for their gigantic props.

Gear reducing is doable. Even more used, and very, very reliable, are belt
PSRU units. Replace the belt at 200 hours or so, and fly with confidence,
if the bearings and such are properly designed.
--
Jim in NC