You do know that Z1 is capable of over 300hp and it is super reliable.
But a turbo rotax would be fun.
Your not going to get 300+ hp out of this motor. The z1 is 125 hp twin at the crank in aspirated configuration which isn't much more than our rotax. You are not going to increase the power to nearly 200% with a turbo. I had a turbo r1 (inline 4 with base Hp of 195) and you don't get anywhere close to that increase over natural aspirated base HP with a Turbo on pump gas.
Beside why would you put a AC twin with the swap cost you would be much cheaper having a more powerful custom turbo on a rotax 1000cc twin built. Next thing you will tell me that the AC z1 Twin is more reliable than a rotax motor...lol
I've seen guys make 500 horse with this engine... It's obviously nowhere near stock since its been bored and stroked and but it can be done... This is proof from Queen Racing in Lake Havasu City. Increase displacement, run significantly higher boost with an extremely oversized turbo, pair with race fuel, the right internals and creative tuning, and it is definitely possible. At median boost ~25psi, they are generating well over 300 horse at the wheels. Apparently on the dyno they've generated over 500 horse @ 40 pounds of boost.
On a side note, OneStopPerformance claims they can generate 700 horse from the Yamaha Apex engine but that's a 4 banger... Yikes!!!