What you have is a Mazda Renesis
engine. (RX-8). Successor to the 13-B engines used in the RX-7
car.
From the "B" stamp and invoice you have a 2:17:1 PSRU (propeller
speed reduction unit).
The "C" PSRU is 2.85:1.
Because the Renesis is designed for somewhat higher RPMs (I think
7,500 is redline in the car?) the 2:85:1 is preferred for the
Renesis, but 2.17:1 can certainly be used too with the right prop.
Finn
On 3/7/2022 9:41 PM, Marvin Kaye
marv@lancaironline.net wrote: