Originally Posted by office888
Even if we assumed Seadog built to a 2:1 safety ratio (which is on the low side, most manufacturers chase a 3:1 or 5:1), that would put even the light duty hinges at 600 lb capacity. Then, we'll assume the load is divided evenly amongst both hinges, so we'll times this by two. Meaning, the hinges would have had to seen in excess of 1200 lb of loading to fail.
If you have 2 or 3 no-so-smallish people on the seat and the boat leaves the surface and slams back down, I could see 1200 lbs being reached pretty easily.
Your math seems very reasonable and believable, though I'm not sure the failure criteria is all that straightforward in realistic terms. It's also going to see some degree of side loading, repeated stress, etc.
But yeah, bottom line is that the supports are pretty underbuilt for serious ocean use...