I'm sorry, I can't help you specifically with the Leopard 40
, but I can tell you this about diesels. In our cat, the engines are midships (which has certain definite advantages, but I won't go into them, here). The only time we've ever smelled the engines is right after I've changed the oil
filters. (My wife also has a sensitive nose, too, and she's been fine with them.) Even then, it only lasts long enough to move some air around. Really, if you smell diesel
in the boat, then there's a leak somewhere. It might be so small in quantity that it aerosols without ever pooling up, but there is something going on.
You might also want to keep in mind the trade-offs involved of having cat engines far aft:
1. You've got the heaviest objects on the boat far out on one end, and this will tend to increase pitching.
2. Some builders (e.g. Lagoon) put the saildrive/prop aft of the rudders, which means that you need to be more careful with reverse in those models (380, 400, 440), not to mention you also have very pricey bits hanging out there quite close to your transoms! Do be careful when docking
aft-first, and definitely do not, do not, like in never, ever, leave dinghy
painters, other loose lines around there.
3. Access to the engine
rooms are usually through hatches in the transoms, which means that if/when you need to get to them in a hurry and if you're in bad weather/following seas, it won't be very comfortable back there and your engine
room will be much more exposed.
Just things to keep in mind. Good luck with your search.