I don't know the yards in your area directly, I can tell you that nearby in RI and MA you'd be paying $90 something/hour for labor. Let's round up to $100 to make the math easy. Let's say 2 person weeks effort to re-power. Why so much, take the old engine out, probably throw out the wiring, probably move the engine mounts which are rotted so you'll get new ones and need to glass them in to fit the new power plant, you'll want new wet muffler (the old ones rotted) and exhaust. You'll want a new control panel. While you're messing around you'll find the thru hull for the engine intake needs to be replaced, you're there anyway so, and some bulkhead will be in the way, and you'll notice that the fuel tank is full of crud so you'll want to replace it, the water separator filter is old, replace that too, might as well replace the fuel line, how old are the batteries......
You get the idea. 80 hours, at 100/hr = 8K. Another 7K worth of parts, you're easily at 15K (not sure what an engine this size costs, but you'll need a surprising amount of other stuff too).
Unless you love it, and it's perfect in every other way, find one with an engine that works and a higher ask. Particularly for new buyers, recommend you find a boat that's regularly used by a meticulous owner, you'll pay more up front but you'll save in the end. The only people who beat this equation are skilled and persistent do it yourselfers. I'm sure one or more of them will chime in after reading this.