How much money are you willing to spend?
Do you plan on buying a new engine or something used?
Have you considered rebuilding the current engine?
You said that you bought it used. Is the rest of the mower in good condition?
My 2021 Gravely ProTurn 260 came with a Kohler Confidant ZT740. This Gravely is a similar size and weight of the Tiger Cat. It has plenty of power. However, the ZT740 is rated at 25hp.
Going to anything above 27hp, you are going to start seeing less offerings with carbureted engines.
B&S Vanguard largest carbureted engine is 26hp.
Kohler offers CV752 for their largest carbureted engines at 27hp.
Kawasaki offers the FX850V carbureted engine at 27hp and the FX1000V at 35hp.
The new Tiger Cat II smallest engine offering is 26hp EFI.
So you could possibly get by with a B&S Vanguard 26hp engine.
Learn about the Vanguard® 26.0 Gross HP* 810cc V-Twin Vertical Shaft engine including Features, Specs and Options.
www.vanguardpower.com
B&S also has the CXi 2700 engine that is rated at 27hp. It is a carbureted engine but, it is also offered in EFI.
<p>These V-Twin engines are specially designed for zero turn mowers and other high-debris applications to endure extended use in extreme conditions. Cyclonic air filtering keeps dirt out and extends engine life. The V-Twin design delivers more power, is naturally balanced for less vibration...
www.briggsandstratton.com
The length of the crankshaft tail piece is critical.