The Catalac has solid fiberglass hulls built double thick, the Gemini a thin cored hull.
Catalacs have a rigid keel.... Geminis use dagger boards.
The Catalac can be found with twin diesel engines (as you pointed out) the old Gemini has an outboard engine.
Catalacs are all over the world ... Gemini ... not so much.
Big differences between the boats. This is sort of like comparing a Land Rover to a Hyundai.
Actually, factually incorrect, and somewhat biased as well.
Even then a modern Hyundai is a better ride than a 1960's designed and built Land Rover in my opinion, and the Catalac is certainly not a Land Rover.
There is no coring in the gemini hull - it's 3/8 thick fiberglass and that's it.
They use plywood pads under the mast step, cleats, etc.., other than that it's a air gap/inner liner, tabs and such - and that's all.
If the Catalac has a solid deck I'd hate to see the weight issues.
All 105MC's are diesel, WB30b's, with a drive leg (plenty of issues there).
Gemini's use centerboards, not dagger boards - there is both a structural and function difference. Either is better for performance than a fixed mini-keel.
Gemini's are indeed all over the world, including on their own hulls.
- former owner Hull # 987 - five years of ownership since new.
We just switched back to a center cockpit mono, primarily for financial reasons. Gemini's will do you fine in the Carib.