Two strokes have problems with sitting. If they sat too long, the seals that separate the working chamber from the outside of the case harden and leak.
Check for how much play the main rod bearing has, the manual will tell you what is acceptable. The little end of the rod usually has a roller bearing which is easily replaced.
Check for cylinder scuffing from people who think the less amount of 2cycle oil you use the better it’ll run which is B.S. Use what they recommend and carry a spare plug or two with you, better a fouled plug than grenaded engine.
Hopefully the engines have never had cox fuel run through them, they’ll run like a bat outta hell, for a while and smell like a model engine running.
You can take the cylinder off easily or look through the exhaust port to see if there’s any scuffing on the piston. I think Yamies use a reed valve which can crack and cause problems or break sending the pieces into the engine but they’re easy to replace and not expensive.
If the price is right, they fire up and run well, who cares about the engines? Every running two stroke failure I’ve had was due to scuffing of the pistons and cylinders and it’s easy to bore the cylinder and get an oversize piston, just make sure the machine shop bevels the transfer ports in the cylinder.
The other failure I’ve had was an Rd350 that sat and its crank seals dried up and cracked. It ran (after being towed) but it sucked in the regular gear oil which is a good indicator you need to get the crank rebuilt which was easy to get done in the 70s. Since yours are from around 2002, I wouldn’t worry about parts and if you’ve never rebuilt an engine, a two stroke is easy, just make sure you put the piston ring gap in the pin in the ring land or you’ll have a bad day.
One motor has 156 hours, and the other has 352.
These are both 2002 Yamaha Waverunners that have seen light yearly use in Lake Lanier Georgia. No salt water exposure.
Hulls are in good shape; reverse works well on the three seater; fuel lines looked good. Bilges looked like 12 year old bilges, but no oil accumulation. Bit of glazing on the dash gauge, but otherwise good. Fired up and ran just fine. No particular smoke when running (water running through the bypass) either at idle or throttle-up or throttle-down. Seemed sound.
Since the price was right for the pair (well under $6K) they are very tempting. Just a bit concerned about the 352 hours on the three-seater.
Also as Lx says, do not take this too seriously. These things soldier and smoke on forever. Rebuild. Enjoy. Buy more.
BTW, this is a pre-purchase question. A “what am I getting myself into?” question.
Won’t have the chance to get into the motor.