Butyl seems the way to go
We re-bedded all of our fixed and operable portlights on our 1990 E38 this summer with butyl tape. Several of the portlights were actively leaking and/or showing signs of leakage, not to mention the white sealant looked moldy.
It took about an hour per portlight to clean off all the original 1990's sealant (5200?), and about 10 minutes to re-install with butyl. About 15 inches of rain so far and no leaks. I'd recommend it. We bought it through here: http://www.pbase.com/mainecruising/rebedding_hardware&page=2
Mark
We re-bedded all of our fixed and operable portlights on our 1990 E38 this summer with butyl tape. Several of the portlights were actively leaking and/or showing signs of leakage, not to mention the white sealant looked moldy.
It took about an hour per portlight to clean off all the original 1990's sealant (5200?), and about 10 minutes to re-install with butyl. About 15 inches of rain so far and no leaks. I'd recommend it. We bought it through here: http://www.pbase.com/mainecruising/rebedding_hardware&page=2
Mark