Don't expect more than 15 years life out
of stock Mazda water O-rings.

Perry Mick has had two second gen  RX7 car engine water O-rings
leak internally. Both were 15 years old. Engines were
otherwise still going strong. Perry not only flies a rotary
he drives them as well.

Use the Creavey teflon encapsulated silicone versions
when overhauling.
http://www.rotaryeng.net/TEFLON_COATED_O_RINGS_IMG4.GIF
http://www.rotaryeng.net/O-ring-size2.html

BTW Perry now has 800 hours on his Mazdatrix
over hauled rotary. It is also cooling perfectly
just like a car engine.

He commuted back and fourth to work in it for a few years.
Here are some recent pictures.

More about the constant speed prop shortly.

Paul