To loud, do they have a better muffler kit - Coleman Powermate Powermate 5000W Generator

Most likely a different muffler is available for easy bolt-on solution. Best way to check is to find model and type of engine and check with engine distributor in your area or the web. Engine model is usually found on the starter/fan cover or the block. The problem is the limited space within the frame of the generator. Other solution is to contact a small engine service center for modification. There are several sources for quiet mufflers, however takes creative installation. Take a look at other generators with very quiet mufflers for ideas (different types of machine may use the same engine so take notice how other types lawn equipment /tools deal with noise ). Some generators are made for camping or use in quiet zones and use other methods for quieting the unit. Still other generators are noisy even with large mufflers. Good luck with your project.