Skeeter SL210 & Yamaha Z200 setup NEED HELP

[191champ]

Couple of items I am hoping to get some help with.
First, what is the vent circled in the picture? is this the water pick up?
Second, when running on plane in a 2006 skeeter sl210, about where should the water line be on the motors lower unit?
Lastly, overall set up, the pics show some dimensions. Does this look right? The boat is a 2006 Skeeter SL210 fish and ski.
It is currently running above the cavitation plate and porpoises like crazy with any little chop.
Motor is a 2006 Yamaha HPDI Z200TXR, boat is a 2006 skeeter sl210 fish & ski. Both are in good shape, just the ride is not good to say the least.
This question is cross-posted on the motor forum. Thanks for the help.

[PSM207]

Your "Prop to Keel" measurement is actually referred to as "Prop to Pad/PTP". IMO, 5.5 inches is far too deep and this is typical of how the SL hulls were rigged. The porpoising issue is also common, however it is not solely caused by PTP. I ran an SL for many years, plus assisted in setting up others. Before diving further into resolving the performance issues with your setup, I need to know what prop you are running and the "Wide Open Throttle/WOT" engine rpms when running this prop. More than likely you will need a jack plate, a planing foil and some cargo weight adjustments. Let's first get your prop and rpm info, then proceed from there.

[191champ]

Prop shows 23-M and nothing more, three blade. At WOT I am reading 5900 rpm and getting around 56 mph. Thanks.

[PSM207]

23M is a good prop. Might need a little work, post some pictures of it.