Can you replace a tsunami 125 seat?
Yes. What are you lookingvto replace, the whole seat or parts.
You need to know the year. Wilderness Systems 125 Tsunami.
Some parts can be purchased directly from Wilderness Systems. TopKayaker stocks original or aftermarket brands and they can help source parts.
The seat cradle is held by 4 bolts. The best way to remove the nut is to use a long metric socket with a 3/8 socket universal joint and a short 3/8 extention. Phillips screwdriver will unscrew the bolt if you hold the nut. That bolt has a gasket, a washer and the nut. Put the boat on its side, put the washer on the bolt and startung the bolt is a balancing act.
I can answer soecific questions.
The problem is finding in stock and at a good price. Seat covers for bottom and back can be found from $90 down to $16. If you get a bottom cover, make sure it has the 4 plastic push pins or order them separate. I found all the parts I needed at an outfitter near in Maryville near Harrisburg, PA, and the prices where better than some prices in line. The bottom frame is hardest to find.