Here's what I did
I had that problem when I bought my boat - here's what I did.1. Made sure there were no leaks in fuel system - had to put new banjo washers and fuel pump gasket to stop seepage onto hot engine.2. Cleaned entire engine and engine compartment with foam engine cleaner from auto parts store.3. Scrubbed bilge multiple times with biodegradable cleaner.4. Removed cushions, washed covers, washed foam cushions with lots of soap/water - let them dry in sunlight for several days. sprayed with Fabreze when I reassembled them.5. Sprayed Fabreze on "mouse fur" on sides of interior - didnt' clean this, but the Fabreze seemed to work.two years ago, no problems, no diesel smell.