New owner of a 1976 37 Irwin Ketch.
I am looking for hatch latches, a bathroom door, and other interior parts.
Also I am reading comments about blue water capable boats, and do not understand some of the comments. My boat weighs 20,000 or 22,000 lbs depending on which data you care to believe. Doesn't the weight of this boat denote stability/strength?
Be kind I am just trying to learn
We all started learning somewhere, and your question is a good one. In a broad general sense, simply knowing the weight (displacement) of the boat tells you almost nothing about either the stability or the strength of the boat. What counts towards stability is a broad range of factors such as the shape of the hull (distribution of buoyancy), how that distribution of buoyancy changes as the boat heels, and the weight distribution.
You can have a heavy boat that carries its weight up high, and which does not transfer its buoyancy to leeward very quickly as it heels and it will not have a huge amount of stability relative to its displacement or drag. To a great extent that is the case with your boat. The Irwin 37s started life as budget oriented charter boats. (Think of them as the Hunters of their day.)
Similarly, strength of dependent on the choice of materials, quality of construction, engineering details, and so on. Its easy to have a heavy boat that is has poor glass work, meaning resin rich laminates with a larger amount of non-directional fabric than ideal, and end up with a comparatively fragile but heavy hull. Similarly, even if the hull layup is adequate there can be engineering compromises in the hull to deck connection, hardware and rigging connections, rig design, and items like inadequate internal framing and bonding, and so on. Lastly it takes time and money to carefully produce a strong and stiff boat, and those will usually turn out to be lighter rather than heavier. Heavier is usually a sign of less exacting workmanship and engineering, which in turn usually translates to less strength, especially over time.
To a great extent the laminate on the Irwins was nothing to write home about, and their hull to deck joints, and rigging connections are generally reputed to be problematic. So while they make great live aboards, decent coastal cruisers and mediocre island hoppers, I would never consider them to be particularly ideal or reliable for Blue Water passage making.