Inland Marine Tube Sealant
Just bought 27 year old riken pioneer for super cheap. Half the boat held air pretty well and the other half lost about half of it's air over 24 hours. First I patched and patched the boat, finding it made a huge difference, but it was still losing some air. Sooooo....i purchased one bottle of the inland marine boat sealant, equally distributed it in the tubes, rolled it around for a couple hours (inflated), and have had the boat sitting inflated under my patio for a week with no signs of air loss. Not sure about the long term effectiveness of this product, but for $40 it definitely is worth a try in an older boat living out it's last river miles in my opinion. Just thought i'd share my experience....