Was reading through a bunch of old threads about Suzuki and Honda based engines available in the HBA world. $10-15k buys you a bunch of R&D and a decent FWF/FWA package at about 100hp plus/minus. So I started looking around at engines (again). What I started seeing is that there is a lot of crate replacement engine innovation going on right now. 100HP/Liter is pretty much the standard now. Direct injection is common. Lots of forums full of tuners out there doing some pretty amazing things with 1-1.5 liters 3-4 cyl inline. A lot of these engines like the Chevy Spark are all aluminum, tiny packages, and over 100hp. There are some heavier larger displacement stuff out there as well for larger packages. Then I started looking at Yamaha and Suzuki outboard powerheads. Same thing. Lots of evolution in the last 5 years. I was just looking for candidate motors that the majority of the block/head/scavanging system/turbo and intake exhaust fits in about 24" high 18" wide 24" long. Seems the auto world has figured out that small, light weight high output reliable engines that can put out a lot of power at a best efficiency point is aligned with hybrid, high fuel mileage goals. Interesting that they are die casting blocks and heads now in high volume on these small engines going into inexpensive autos in Asia. Certainly they are not developing this stuff for the bloated USA market. I can grab a complete engine off of ebay running, low mileage for hundreds. Not a bad platform to experiment with. 100hp turbo 4 stroke well under 200lbs... possible? Rotax already makes a box to bolt up.