The Mercury 250 Opti is a potent direct injection motor. Be sure to use the appropriate Mercury/Quicksilver oil for the Optimax as well. It's not the same as the 240EFI.
These motors are durable, when taken care of, but very expensive to fix if they do break down. If you are not handy with a wrench, I would strongly recommend looking for a local BRP dealer that has been well established for years. As the newer dealers will avoid a Merc powered Seadoo like the plague. Some Merc dealers will work on them, but they see a Seadoo logo and may walk away as well. Annual service is a must, and it will make it a solid boat for years.
It literally is a V6 outboard powerhead on a SportJet pump. With that in mind, read through the winterization procedures as there is gear and stator oil that should be changed annually. If you are in a cold climate, it's a must, as water in there will surely freeze and cost you tons to repair.
There is also a spring-loaded, hinged grate on the intake. Be sure there are no broken tines, or check to see if it was swapped out for a fixed grate. This is called a Hydro-Surge grate and it allowed weeds to pass through the pump. It did work, but the tines were prone to slam back down, break off and go through the pump. And if it is missing tine ends, they may have passed through and damaged the pump liner or impeller. Look for heavy gouges or scratches. As it's a stainless steel liner and expensive to replace. Repairs have been done with JBweld and sandpaper, but it is a bandaid fix.
If it is heavily gouged, you will experience cavitation upon take off. This boat at 20' should jump up on plane very easily, and top out at 50+ mph. The boat itself is pretty solid and one of the most solid 20ft hulls for it's vintage. It's a great layout for a non-tower bow rider.
Good luck.