The Athena does have the engines under the aft bunks. Initially, I would have preferred access from outside but have changed my mind with experience and input from our charter
company who maintain a number of FPs.
There are several problems with access from the transoms. First, the machinery suffers considerable corrosion
problems despite attempts to improve sealing. Second, the access in a seaway can be exciting at best and hazardous at worst. Third, access for maintenance
is limited, I did not envy the guy trying to change the calorifier
on a Lavezzi
Yes, it is a pain getting to the engines but with a little bit of work that can be real easy. The real problem is as you lift
bunk board it drops off the battens as it fouls the trunk at the outboard
aft end. My solution is the split both the inboard and outboard bunk boards transversely about 300mm fwd of the aft bulkhead, hinge them there and then fit gas struts that will hold both bunk boards with cushions
on up against the headlining. That makes routine maintenance
easy. All you will need is 8 gas struts, some batten and hinges and cost about GBP150. The trick is getting the gas strut force right. For that you will need a spring balance and some high school
Of course, you can cut the cost and doing the mechanics calcs by using low tech wood props.