I’m not familiar with Viking hatches so apologies if I’m going down the wrong road here…
I bought “rubber rope” online, you can get various diameters/profiles, and it worked perfectly to reseal hatches. You may need to soak it in hot water if you need it to be more compliant as you fit it. There may be a little trial and error with the size you order to achieve the best fit.
Leave the joint at the bottom where leaks are less likely, unlikely the boat is filled with water of course…..
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