To clear up my statement, yes the New G230RC does has 3/10 more hp than the CY 23.
For the RC Airboat I still stick to what I have said the CY is my engine of choice. My opinion is based on information, research from places that sell these engines.
Information from DDM
CY23RC 2.5 HP Engine - $149.00
Chung Yang CY23RC engine (32mm bore, 28mm stroke - 22.5cc) with Walbro WT-668 carb. 2.5 Horsepower. Similar design to the Zenoah G230RC - 4 transfer port 32mm cylinder, single ring piston, double sided finned flywheel, and HP exhaust canister. Ready to bolt-on. All parts are interchangeable with the Zenoah G230RC.

G230RC 2.8 HP Engine - $195.00
The brand-new 2005 Zenoah G230RC engine is a 22.5cc (32mm bore, 28mm stroke) performance machine. The engine features a stronger intake manifold for better thermal isolation, a red silicone spark plug cap, new blue gaskets, wider intake and exhaust ports, a lighter 32mm piston and thinner ring for reduced reciprocating mass, and improved transfer port matching between cases and cylinder. This engine offers serious performance. It features a 4 transfer port 32mm cylinder, Walbro WT-603 carburetor

CY27RC 3.25 HP Engine - $164.00
Chung Yang CY27RC engine (35mm bore, 28mm stroke - 26.9cc) with Walbro WT-668 carb. Includes 54mm inner clutch assembly pre-installed. Ready to bolt-on. 3.25 horsepower. Similar design to the Zenoah G230RC/G260RC - 4 transfer port hp cylinder, single ring piston, double sided finned flywheel, and hp exhaust canister.

G270RC 4-Bolt Engine w/Full ESP Porting 4+ HP - $439.00
The brand-new 2005 Zenoah G260RC engine is a 25.4cc (34mm bore, 28mm stroke) performance machine. The engine features a stronger intake manifold for better thermal isolation, a red silicone spark plug cap, new blue gaskets, wider intake and exhaust ports, a lighter 34mm piston and thinner ring for reduced reciprocating mass, and improved transfer port matching between cases and cylinder. This engine offers serious performance. It features a 4 transfer port 34mm cylinder, Walbro WT-603 carburetor


G260RC 3 HP Engine - $214.00
The brand-new 2005 Zenoah G260RC engine is a 25.4cc (34mm bore, 28mm stroke) performance machine. The engine features a stronger intake manifold for better thermal isolation, a red silicone spark plug cap, new blue gaskets, wider intake and exhaust ports, a lighter 34mm piston and thinner ring for reduced reciprocating mass, and improved transfer port matching between cases and cylinder. This engine offers serious performance. It features a 4 transfer port 34mm cylinder, Walbro WT-603 carburetor

The most recent testing I have done myself personally, was a speed comparison between a stock CY 27cc with the exception the carb was replaced by the walbro WT-813 and a CY29cc with the stuff crank and the walbro WT-813 carb.
Now I'm sure if you was to place each of these engines on a dyno the 29cc will show to have more hp than the 27cc.
The speed difference test was done on the same cajun gator rc airboat, same day, just a few minutes apart (5 minutes to change engines)
Result, top speed for the CY 29cc was 33.5mph top speed for the CY 27cc 36.6mph
Again as I stated the Zenoah is a very good engine.