Damn if that's really your dad's first time riding a stand up that's incredible. I just got a mint 2019 superjet. It's my favorite thing ever. I paid a lot for it. 9.5k. But worth it.

that superjet is a great ski to have. Yamaha made the 701cc 2 stroke (nicknamed the roundnose) superjet for nearly 25-30 years and only changed very minor things about it because of how great of a ski it is. they only recently stopped making the 2 stroke model in 2020  because of emissions laws but to this day, many hard core riders still ride these superjets exactly like you have. unless you're planning to move on from jet skis, I'd keep that SJ if I were you. its getting increasingly harder to find those especially in the condition yours is. if you get serious enough, start looking for a backflip ski like a rickter ;)