To increase the weight limit on your kayak, you will need to make sure that it is wide enough to provide adequate stability and has a weight capacity of at least 300 pounds. You should also look for a kayak with comfortable seating and that is easy to get in and out of. Additionally, it is important to practice getting in and out of the kayak on dry land to make sure that you can do it safely and easily. Finally, if you are paddling in open water, you should consider using a companion kayak for added safety.