TL;DR Everything we see in real life, what we read in the books, and certain aspects of the game being part of cannon,(John is either skinny for his height, or the armor is super thin for him to look how he does with the armor) John is either between 350-400 pounds(looking like a normal 6’8 human weighing 175-200 pounds), or 500-600 pounds(looking like a normal 6’8 human weighing 250-300 pounds) without the armor.
So, I was trying to look up the original material from the books(not the reprints) on the height and weight of a Spartan. I do in fact remember reading 117 to be 6’8 without the armor but I can’t find the weight. I think it was said to be at between 300-350lb’s. Reading the part in “Fall of Reach” after the bit where John, Sam, and Kelly capture the flag, Mendez mentions they can " lift three times their body weight- which, I might add, is almost double the norm due to their increased muscle density". Martyn Ford who is 6’8 is 325’lb’s, proves that they can be that heavy. Now Ford IS a body builder, and the tallest body builder, Olivier Richters, is 7’2 330 pounds(so miss me with that "6’10 290pound bs, that’s a stick). Soldiers do not train like body builders, so even though they can be stronger than a body builder, they don’t get as shredded, but the weights may be similar, so it is not too farfetched to say John is 6’8 and 300 pounds at least. If we are to believe the quote from the book, that would mean John should actually weigh in at 600 pounds! Well, his bones, nerves and vascular systems from the augmentations should, if not, would support that weight. Per the quote, he would be able to overhead press 1,800 pounds! If you look up what is a “classic lift” a bench press is not mentioned. So let your imagine run with that.
All that is consistent with the fact that he kicked a MK1 Exo Skeleton 8 meters, and they used one as a counter weight. It is also consistent with how much the suit amplifies their strength to be able to flip tanks. It is also consistent with the fact that right after his augmentation, at 14 years old he already looked like a jacked Olympic athlete (CORRECTION: he looked like an Olympic athlete even before the augmentation). Three weeks of recovery, and at that “weakened” state he was already stronger than ODST’s that look like Ford, evident by effortlessly rag-dolling them, and consistent with the “three times their weight, which is doubled” quote.
Given all that, it would not be too “out there” to conclude John could weigh up to 600 pounds. But that is not a number I remember at all. I remember ~300. I made another thread concerning how small he has to be though, considering his arms, with MJOlNIR look only a bit larger than a regular marines arms. Looking up more reference photos, I came across a guy who is 6’4" and 194 pounds. Ripped, but skinny. His size is consistent with how Chief should look without MJOLNIR considering the armor has to be thick enough for the tech, and protection it provides. His “small” size would be consistent with both quotes from the book. If he looked like a normal 6’8 Human who weighs 200 pounds(I added two inches, and 6 pounds from the reference) this means John would weigh 400 pounds, while being able to lift 1,200 pounds, and that is without ever hitting the gym! Given the info from the book about being double the weight, people saying he weighs 290 pounds even at 6’8 would mean he would look like a normal 6’8 human weighing 145 pounds. That is severely underweight.
Everything we see in real life, what we read in the books, and certain aspects of the game being part of cannon,(John is either skinny for his height, or the armor is super thin for him to look how he does with the armor) John is either between 350-400 pounds(looking like a normal 6’8 human weighing 175-200 pounds), or 500-600 pounds(looking like a normal 6’8 human weighing 250-300 pounds) without the armor.
Everything here is consistent with what we read in the books, and see in the games concerning their strength, speed, and how much the armor amplifies their strength and speed, and with what we observe in real life pertaining to the height, and weight of people who workout for competition, fitness and combat respectively.
This was fun.