I wouldn't think it would be too much trouble to put in new butyl tape and screw the hatch back down, even if it is only temporary. Then, you'll know if your problem is from old butyl tape or something else.
The plastic hatch frame will break apart when I take it off the trailer. I'm pretty sure of it. And remember, this trailer was stored inside for the last 7+ years. It supposedly did not leak last year when the former owner got caught in a rainstorm. But maybe he didn't really pay attention. I just brought the trailer home on Friday. So it's really the first time it's been outside.
It's old butyl for sure, compounded by added sealer of some sort. I have to get all the old sealer off...which will be the hardest part. Well, besides finding the correct size hatch.
And I am gone 12 hours a day for work for the next 4 days. My plan is to determine the hatch size if possible, or see if I can order 2 that are closest..wait til they are in at CW, then get the parts, tear out the hatch, and try the closest one in after seeing the opening. If it's a go, then I'll spend the weekend trying to get the old sealer off. Then re-tape and seat the new hatch.
I'm just going to have to plastic up the hatch until then, and if we have rain I'm going to try to hit the Dam with plastic and tape and hope it works. I just need 3 clear days on the weekend to get this hatch off and the new one on. IF I can get a new hatch that fast!