Well, as Shrew said, it is no longer listed so I guess it does not matter much anymore
In my personal opinion a 4.3 is a bit small for this boat. It really does depend on how you plan to use the boat though.
So what uses to you envision for your next boat? Do you plan on just cruising around? Do you plan on watersports such as tubing, skiing, wakeboarding?
If just cruising around the 4.3 will be fine. Not the fastest out of the hole or on top end but you will appreciate it when it is time to fill up.
If skiing is planned, I think you need a V8 for that size boat. You can change props to help on the holeshot but at the end of the day, you are limited on your torque with the 4.3 and will struggle to pull skiers out of the water if there are a few in the boat and the skier is not a child. I think you would do best with a 5.0 or better yet a 5.7 for the 19-21ft range. If in the 17-18ft range a 4.3 or 5.0 would be ok.
Tubing and kneeboarding does not take much power so the 4.3 would be fine for either of these activities. I have no experience in wakeboarding but would not expect it to be too demanding, probably less than slalom skiing for sure since the board is pretty wide.
I grew up slalom skiing so I do know what kind of power you need to yank someone out of the water here