re: Buying an old arse jet ski more headache than it's worth?

If it has good compression, minimum 100 psi each cylinder and only less than 10% between cylinders, I'd play with it. Old YAMAHA skis are pretty reliable. I have a 1996 Waveraider 1100. It's fun and has way less complicated features than newer skis of today. If you've rebuilt 2 cycle engines, these aren't much different. In fact, unlike an outboard, motorcycle, or a car, there is no water pump. The "jet" forces water through the engine. In some ways they can be simpler than what you might be used to