Hi Marty, Thank you for the welcome. I did not build my airplane. I bought it flying. The registered E.W. is 605 lbs. The fellow that did the build strengthened the firewall in a couple of places and Zenith provided the engine mount. The engine is bare bones, no starter and has a B&C lightweight alternator (12 amp) Slick mags (lighter than bendix) and bare bones electrical. With no starter, a motorcycle battery (approx 5 lbs)in the back suffices for all electrical needs (flight/com 760 radio/intercom). I have a metal prop 68x40 that weight about 22 lbs.
I've not flown the plane that much but the C.G. is comfortable and it trims well. I'm old school and grew up with the little Continentals. I had an 8E luscombe for years and used it to commute to my job, so I am a little bias and still consider the Rotax a snowmobile engine. That probably isn't fair because I rode snowmobiles and have not flown anything but turbines for 35 years, and in my research the newer Rotax's look like a good engine. Must be a generational thing.
When I retired I went back to our local community college and took a 2 year course to get my A&P ( kind of interesting, I heard " who's the old guy" quite a bit !!) thinking I would build an airplane. Good sense prevailed ( I Hope !) so I've decided to fly and maintain instead. The Continental is much easier to maintain and price wise they seem to run neck and neck with the Rotax. I would like to say apples and oranges but what I've found is as follows:
My Continental is less than 200 LBs. with the prop it is over that.
The all-up weight of the 912 is within 20-25 LBs. of the Continental in some cases on par.
The Corvair and other auto variants are over the 200 LB. magical number but a lot of guys are flying them in 701's. I didn't even consider them because their is just something wrong with a car engine in a plane !!!! Old guy thinking !!
My own opinion, A C-85 or a C-90 Continental will perform just as well as an 0-200 on a 701. (You can only push a boat hull so fast regardless of power ! )
Continental fuel burn will be greater with normal operations.
Any engine that will get a 701 into the air makes for a really fun airplane. ( with in reason).
What the future holds for my airplane : Wood prop, will save 10-12 LBs. will move battery forward so it is easier to maintain.
Going with a sky-tec starter
Strengthening a few points on the airframe and nose gear. ( Living in the helicopter world for 30 + years has shown me that there isn't ANYTHING on ANY airplane that is built strong enough !!)
I hope this helps. I am really a beginner on the 701 but if I can help, please feel free to call on me.