I have a 2005 21' pontoon with a 60 hp Yamaha. I've been battling pin holes in both pontoons ever since I bought it used about 5 months ago. Yesterday I picked the boat up in my lift and it was tilting to port. This has happened before to me, so I'm aware of the process: remove the drain plug, hook up the compressor to get 4 psi, and start sparying on soapy water to find the hole. This time, I hooked up my compressor first without draining since I thought the extra 4 psi would help to drain the pontoon. So, I used an aluminum rivet to seal the hole. Then I removed the drain plug and water came out. I thought I was done, but my pontoon still lists to port! Previously, the pontoon was pretty even when I thought I had water out from both. Can there be water trapped inside the pontoon somewhere? Are there compartments in the forward part of the pontoon? Do I need to drill a hole in the forward most section of the pontoon and drain?