Effect of power loading on Vy ?

[Trolltuner]

Vy increases with weight, decreases with altitude. But what, if any, effect on Vy occurs with a change in power loading?

Example: A Cessna 182 w/MTOM of 3100 lbs and a stock, 230 hp engine has a power loading of 13.5 lbs/hp and a sea level Vy of 80 KCAS, decaying to 73 KCAS at 14,000 ft.

The stock engine is replaced with a 300 hp IO-550, and power loading becomes 10.3 lbs/hp. Obviously, the airplane will climb better at the same Vy. But is there also an effect to or change in Vy due to the power loading delta?

And a related question: Is there a way to reasonably approximate the correct decrease in Vy vs. altitude?

Thanks!