You are right on Peter Brian Eiland www.RunningTideYachts.com distinctive expedition yachts > other than docking, you need about two people. In the open ocean, it doesn't take much to keep a functioning boat headed in the right direction. The problem is indeed close quarters, logistics, and mechanical aptitude. Large boats often have multiple electrical systems (12VDC, 24VDC, 120VAC, 240VDC, sometimes 3-phase). Sophisticated hydraulic systems with valve farms that resemble a nuclear reactor. Shafts, couplings, steering linkages, etc are all designed differently and require different tools and knowledge - along with brute strength to handle. There are lube-oil reservoirs and centrifuges. Multiple generators and massive electrical transfer panels. Head systems are typically different. A/C and heating may be much larger. Even fresh water pumps are different on large boats. This is all special knowledge that isn't acquired at a 2-day diesel engine seminar. Depending upon configuration of the boat, docking may be a realy challenge - an 80-foot sport fisher has great access in/out of the cockpit. But a motoryacht style boat may need the companionway steps lowered in many instances - it helps to have a nimble deckhand (or two) who can scramble around. And that's not to mention any differences in USCG requirements (like lights). When the boat is in top condition and everything is working well, 2 people can easily run it (though they had best be near-professional crewmen), perhaps even dock it in the right conditions and location. But how often are the stars lined-up so perfectly? I heard a knowledgeable boater observe a long time ago that 70-foot yachts are awkward - too small for professional crew, too large for the average couple to operate comfortably. While bow/stern thrusters and electronic navigation systems have helped, running a 70-footer is not trivial. Peter