Speaking as someone 6'9" and 200, 39" inseam, there's several options, but he (as I) will likely be underweight on anything "playful" and on the light side on most boats. Which is fine. In the smaller/playboat arena, the following should fit easily:
- Jackson Superfun (my small boat of choice).
- Jackson's 2015 4fun (not sure on the earlier ones)
- Liquid Logic Freeride 67 (slightly smaller than the superfun, but I can fit it)
Fluid has some playboats Leif fits in at 6'7", so your son might. I don't.
The SuperFun was/is my boat of choice for many years, it's a great all around riverrunner/playish boat. It fits me better than anything else and is comfy enough i can sit in it all day.
For more of a riverrunner slant, the boat I'm thrilled with and I think is an amazing tall and thin guys boat is the 2014 Burn XL. This is the first boat I've bought that I don't have to do any customization other than adding 1.5 pieces of foam into the hip pads (and they're not bulging massively either). I have the buikhead one notch futher than Pyranha woudl likely say is ideal, but your son shouldn't need it. It's a great river runner, surfs nicely and a decent creeker. This is a much better fit than the 2010 Burn is for a tall/thin guy.
While I like the Karma, the large is a very wide boat and he'll need lots of foam hip padding to fit it. I find it makes it a bit harder to roll than other boats I've had, but I do like how it behaves on creekier water more than the Burn, mainly as it's got less sharp edges. If he can fit the medium Karma, I'd give it a shot too. It's the width of a boat I need, the bulkhead is just too short for me (and cannot be removed like I did with my '10 Burn). The other boat that I fit would be a Pyranha Shiva. It's got a cockpit very similar to the new Burn, but is a displacement boat. It should be easier to roll as a result of that than the Burn, but I think the Burn's a better riverrunner.
For multi-day, so far it's been the Remix XP10. Though I'm not a fan of LL outfitting. The Karma RG is too short, though it may work for your son. It'd be borderline I suspect.
Aside from that, get out and try climbing in. For me I've liked boats with supersized cockpit openings, which has limited me to Jackson and Pyranha. It just makes getting in and out of the boat much easier.
Good luck and have fun!
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