As far as smells -the better the ventilation, the fewer the smells.
I have found that Nicro type solar powered fans running 24 -7 can help in the head area.
It's the waste hoses that typically start to smell bad after 30 years of wear. Only flushing the head with fresh water as opposed to pumping salt water helps reduce the smells tremendously, but uses precious tankage. In the bilge, drain & mop it well, & clean it up with a lil' bleach solution to kill the bacteria that make the smells less obnoxious. Spray febreeze on ol' coushions helps. As far as diesel - if it smells it probably has a minor drip or seepage leak somewhere. Mine had a smell of diesel odor -one drop can reek! & sure enough we found a tiny seepage point at the fitting near the fuel filter. Check all fuel clamps religiously for leaks & you'll probably find one. You nose knows if there's a problem. But that old boat smell is something I kinda miss after I'm away from it 4 too long. Call me crazy. Cheers.
