You're in luck, actually
I had a Merriman/Yacht Specialties steering system on my Aquarius 7.0, and have some pics, though they're not very good. Assuming yours is the single push-pull cable with a chain drive to the cable inside the pedestal, it comes out the transome through an angled bulkhead fitting with a big nut on the outside. The cable itself is never visible on the outside of the boad, but a guide tube of sorts slides in and out of the sheath to push/pull the rudder.
I took mine out of the boat partly because the cable was too stiff and required a lot of effort to turn the wheel. I tried to lube it, and put a lot of time into it, but never got it to work as well as I thought it should. I could not find a replacement of that size (it's a larger diameter than just about every cable out there), and went directly to every cable manufacturer I could find in the industrial directories. I went back to the original tiller steering, and liked the increase in cockpit space.
After I sold the boat, and purely by accident, I was talking to the tech folks as Edson about my H340 steering (wheel was never properly aligned with the rudder) and mentioned that I had a Merriman system that I took of my small boat because of the cable. He told me that they stock them in two lengths, and he correctly cited the correct end fitting diameters and types! Not too expensive, either. They bought out Merriman and killed the product line long ago, but it would seem they still sell control cables for them.
I still have the wheel and pedestal, and the old cable, in storage. If you need to see a pic of what the end of the cable is supposed to look like, I can take one and post it, but the fitting for the boat is in the (fuzzy) pic I'm posting here.
