There has been an interesting thread/discussion over on the Power Catamaran mailing list that hit on engine room access and the safety issues involved. Several points came up that had not always been obvious to me (experienced people often learn things the hard way… lets try to learn from their issues :-)).
Engine room access has trade-offs just like everything on a boat. Interior access can allow smells/dust/dirt/leaks into your living space. On the flip side it allows you to access the engine room out of the weather. Some of the popular "transom" or "cockpit hatch" access methods could leave you in an exposed position if you’re trying to affect repairs in bad weather conditions (when it often seems to happen). That nice big hatch that lets you have full standing room access and plenty of light will let a lot of water in the boat if you are getting a big wave over the side. A combination of a "bolted" hatch for major, at the dock repairs and a less convenient but maybe safer interior access could be great. Other’s argue that having the engine room sealed from the living space means a leak (stuffing box/shaft, etc.) means flooding just the engine room, not the entire boat. That’s a good point, but again, trying to deal with the leak in bad weather and heavy seas strictly through a deck hatch can be an issue. Much of this discussion centered (obviously) around the needs and design constraints of a power catamaran, but much holds true for many other yachts.
Another item is fall hazards. I’ve known people injured falling through openings in the floor/deck. I’ve read of other serious injuries on similar falls. Having a cabin sole hatch removed while you work is something to watch for at all times. Its too easy to get "used to" the hole in the floor and then stepping back into it.
Smaller, coastal and inland boats probably don’t have all of the issues of a blue-water cruiser, but its something to keep in mind. Outboards are fairly reliable, but we’ve probably all had to work on one… usually at an inconvenient time. The people such as the Bartender crowd with outboards in wells where they can tilt them back "over the deck" point out that this design can at least help with the "dropping parts/tools in the water routine". Hanging over the transom trying to get a motor running in bad weather isn’t exactly the safest position to be in.