Hey,
AFAIK the only way to clean the bilge is to use lots of water, lots of degreasers, and lots of elbow grease. And for many bilges, long arms and don't be squeamish!
Once the bilge is clean you may still have to deal with odors. It's common on many boats to have mold growth in hard to reach and hard to clean areas. This includes all of the hidden spaces like compartments behind the settees, under and around water and fuel tanks, under the vee berth, etc. It's hard, like REALLT hard, to get and keep those areas clean. My quick and dirty method was to spray bleach into those areas and wipe with a rag. I was never able to get those areas really clean, but by keeping the mold down and trying to get air flow into those spaces, the odors eventually mostly vanished. I did have to spray the cushions with fabreeze every spring and fall.
Good luck,
barry