Tea pot carb help

[tjfl]

Have a 52 Merc with a tea pot carb. Will idle perfect but die shortly after giving it throttle. Found the diaphram cracked for the power valve. Currently looking for a replacement - hopefully will correct the situation. I'm totally ignorant on this style carb and see no point in replacing but I'm open to an alternative replacement if it's more reliable and cost effective. Any advice is appreciated. Thanks, Tom
PS. Running an electric pump with a regulator set at 2 1/2 psi. Fuel tank has been drained and is clean.