access, yup, that's a dilemma. If the engines are under the aft berths, then you get access to them out of the weather
, but then you get to live with more noise
and smells in the interior
. Put the engines in their own compartment further aft and you get reduced noise
and smell, but then you get more exposure to the weather
in the situation you describe.
Pick your poison. In all the 38 to 46 foot cruising cats I've been aboard (and I've lost
count), you had one or the other (although a few have had both). Unless you decide to go electric
, and that has other risks, already amply discussed.