For all of those that have bought a used boat out of state, I know everybody says to have a mechanic look over the engine and perform all tests/diagnostics to ensure it's sound. How do you set that up, and how do you ensure the boat gets looked at when it's located 5-8 hours way? Thanks for the help!

Don't

I drove 4 hours each way 2 times to purchase my boat. It was still in Texas, but a ways away. I went and looked, inspected, drove the boat, then had a mechanic completely go through the boat. I liked the boat, left a deposit, got the paperwork going, drove home, came back to pick up when paperwork was done and everything we discussed that was wrong was fixed. After this I would never buy a boat sight unseen. My boat looked perfect in the ad, it had a few small issues that needed attention. My boat was a1owner 2010 Ranger with super low hours. Maybe a newer boat would require less diligence, but better safe than sorry.
This was all 3 weeks ago. Loving my new (to me) Ranger Z520C, but would have been disappointed if it showed up like they were selling it. Speedo did not work, 1 power pole had hydraulic fluid leak, the stern mounted fish finder had a short in it and would cut off when bouncing in waves while driving, 1 gas cap was cracked, the passenger grab handle was missing the rubber grip, and the cover was torn/replaced at my request with a new Ranger Cover, plus I got a spare prop, all fishing boat ropes, anchors and other stuff that the seller would have kept by simply asking "does all this come with the boat too?".
Good Luck with your purchase!

What kind of boat are you looking for? Price range?

Phoenix 920 or 921, 2014-16. IMO, and from what you'll see on BBC, a 2014-15 920 shouldn't be any higher than 55-57k, so that's my upper range.

I bought my current boat from an owner in Tennessee, and had no problems. The owner should have his state registration card, which has all the required documentation for TPWD.

I found mine on craigslist, and had the owner send me about thirty pictures, then I located a marine shop in a nearby town and had the owner take the boat there. I asked the shop to check ecverything with the motor, compression, bleed down, lower unit grease color, etc. the shop was also affilated with a fiberglass repair guy, so i contracted with them to check over the hull, top cap and transom.

When you have checked out make sure all reports back to you are in writing on their letterhead of shop ticket, pay with a tracable cashiers check. If the boat does not turn out like they said you have better record of payment.