Kokko, permit me restate that summary a bit more precisely.
The "law of the land" is defined in the
USCG NAVIGATION RULES AND REGULATIONS HANDBOOK which contains both the
International Regulations for Preventing Collisions at Sea, 1972 (COLREGS or IRPCAS) and the
Inland Navigation Rules. These two sets of navigation rules are very similar, which one applies depends (roughly) on whether the particular waters are reachable by seagoing ships or not. (There is a set of precise boundary lines defined).
The Navigation Rules do not distinguish between human powered and engine powered boats. But sailboats (while sailing) are subject to different rules, as are various types of boats constrained by their draft or their activity or other circumstances from maneuvering freely.
No boat has a "right of way". Instead, one boat is the "give way" vessel and the other is the "stand-on" vessel.
- The give way vessel has to keep clear, and is supposed to maneuver in ways that are easy to spot (large changes of course).
- The stand-on vessel is supposed to continue her course (in a predictable manner; this requirement is not always limited to strictly maintaining an unchanged heading).
All boats are supposed to avoid situations that could lead to collisions and to keep a good lookout.
While you are
sailing, when you meet an ordinary powerboat, you are the stand-on vessel. They are supposed to keep clear. If they don't, you are allowed and required to take last-minute evasive action. If you
overtake a power boat (come from more or less behind and are going faster),
you are supposed to keep clear. (Yes, probably not a common scenario, but I have outsailed a barge once...)
You are the give-way vessel, if the powerboat is
- not under command,
- restricted in their maneuverability, or
- engaged in fishing.
There is no reference as such to "working boats" in the rules, except those that are engaged in activities or have deep draft that do limit their maneuverability. Note, that small boats and
sailboats are explicitly required to not impede larger boats in narrow channels.
However, it's simply prudent and courteous to not sail in the path of someone doing a job, if you can avoid it, and if that someone is a HUGE SHIP, then it's definitely the smart thing to do. (That is often called the informal "law of tonnage").
There is one final rule: if you sail anywhere where there are "traffic lanes" demarcated in the water (traffic separation scheme) then you are
- supposed to stay outside
- only cross with your hull at right angles
This may not apply on your typical lake, but is not uncommonly encountered in coastal waters.
This is it for a summary; like all summaries, it glosses over some details, which is not to say that some of these details aren't important.
If any of this was news to you, then going to the source and reading the HANDBOOK would be recommended.