Easy answer.  Yes, MKIIs are blue-water boats insofar as they carry a CE "A" rating, meaning they have unlimited ocean capabilities.  This means that structure, equipment, and rigging are built to a degree that they are expected to survive anything other than "abnormal" sea states (hurricanes, etc).  We moved from a double-ender 22,000 pound Southern Cross 39 to a Catalina 36 MKII and never felt the 36 was at a significant sea-keeping disadvantage.

Although the MKII might be ocean-capable, your personal comfort may be tied to the size/mass of the boat, your age, and the stuff you want to carry, like tankage and storage.  In general terms, sea motion improves with length and weight.  The internet is full of opinions on keels, rigs, freeboard, sterns, entry, weight, etc.  All have trade-offs.  You have lots of choices.

My fellow Portland Yacht Club member Craig Mortenson took his Catalina 36 Mk I 'Patriot' around the world in an unusual way. He says that he hates to be on a boat for more than about two months, so he would pick a good weather window and sail the boat to a desired destination; then he'd come home to Portland. When the weather window was fine for his next leg, he'd fly to the boat and sail that leg. Then he'd fly home...et cetera all the way around. He says that he was in no major storms for the entire circumnavigation.

His one major problem was a collision in the middle of the night with a whale. The collision bent the prop shaft so that he couldn't motor, and bent the rudder to 'lock' it slightly off center. This happened (if I recall correctly) somewhere around New Caledonia. He jury-rigged a rudder and sailed for four days to near the Great Barrier Reef, where the Australian coasties came out to tow him through the maze of reefs to a boatyard where repairs could be effected.  

(There's way more interesting stuff to hear regarding his circumnavigation that makes sharing a beer with him well worthwhile. Examples, his method for getting crew for those legs where his PYC buddies couldn't break free; and a near 'brush' with pirates.)
 

Nick

Curious if you know if the Mk1 or MK1.5 had a CE rating or if construction details between the models made one more seaworthly over the other.

Boats sold in Europe must comply with one of four design categories as noted below. The Catalina 36 Mk II (and possibly the Mk I, but I didn't have access to that spec) is certified as a 'Category A - Ocean' vessel.

Seaworthiness Quantified

The following four CE design categories help to quantify a boat’s degree of seaworthiness, based on the wave height and wind speed the boat is designed to encounter and handle. The further offshore the vessel is expected to venture, the higher are the expectations for construction strength, stability, freeboard, reserve buoyancy, resistance to downflooding, deck drainage and other seaworthiness criteria.

CE Categories from A to D

Category A — Ocean. Category A covers largely self-sufficient boats designed for extended voyages with winds of over Beaufort Force 8 (over 40 knots), and significant wave heights above 13 feet, but excluding abnormal conditions such as hurricanes.

Category B — Offshore. Category B includes boats operating offshore with winds up to 40 knots, Beaufort Force 8, and significant seas up to 13 feet.

Category C — Inshore. Category C is for boats operating in coastal waters and large bays and lakes with winds to Force 6, up to 27 knots, and significant seas 7 feet high.

Category D — Inland or sheltered coastal waters. Category D is for boats in small lakes and rivers with winds to Force 4, up to 15 knots, and significant wave heights to 18 inches.

While the European standards are no guarantee that a boat will be suitable in all respects for the conditions in its designated category, they help to separate the purely inshore craft from those capable of operating safely in more demanding conditions.

Larry thanks for the explanation. It would be interesting to read up on how a boat model is tested for a CE certification

It's a funny thing, perspective!   We've lived aboard our Mk I a total of about 4.5 years of the last 11, making four six-month trips to the South Pacific Islands from New Zealand.   Most of this has been just the two of us, and we are happy not to have a larger boat for what we do.
If we had more visitors, or routinely had crew for passages, we would like more space.   We don't intend to do this.
A 'small' boat like ours is about as expensive as I am comfortable with in terms of maintenance, and with just us a larger boat would make us more dependent on electrical assistance for furling, etc.
When we see some smaller boats in the 25 foot plus range, we wonder where they store everything, we have used every corner we can find, just about :-)
All the best, fair winds...
 

The previous owners of my boat sailed her from California to Tahiti, from Tahiti to Alaska, and from Alaska back to California. They then trucked it to the Mississippi River, sailed out to the Gulf of Mexico, around Florida to the Bahamas, then up the East Coast all the way to the Hudson River, demasted, went through the Eeri Canal, circumnavigated the entire great lakes, and then put her back on a truck back to California, whereupon they sold it to the guy I bought it from.

Joel

Did the previous owners make any improvements or changes to your C36 before taking their extended cruise. I sail Caprice in some nasty weather in the Gulf of Mexico and out in the Atlantic with no changes in the boat from the way it came from the manufacturer, except I replaced the mast and rigging after damage caused by Hurricane Charley in 2004.

Interesting reading for a new 36 owner.  It seems the real question is whether someone is a bluewater sailor not particularly if the boat is (within reason of course).  Seems lots of people have done what they wanted with their 36's.  Sailing form Ca to Tahiti to Alaska,   multiple trips from NZ to the south Pacific, sounds like the boats are doing just fine....