Bill Daniels wrote:

They feel their engine would make a near
perfect tug engine.

Surprize! :-)

A rumor is ...

So much for "practical information".

Diesels make power at lower RPM's than a spark ignition engine so they can
use larger, quieter, more efficient propellers.

There isn't a requirement anywhere that propellers have to be direct
driven. Actually, the only diesel flying today uses a gearbox.

(Sorry for my unfair quoting, but I couldn't resist.)

Stefan