The tool to flare cost the most, I had to buy one to install 2 my self
https://www.amazon.com/Flanging-Tool-inch-Drain-Tube/dp/B002MJDNV0/ref=sr_1_121?keywords=transom+drain+tube&qid=1690888548&sr=8-121
Could try and flare some more to seal or better yet, remove, clean, use sealant and reinstall