i have just a smuch teak as you if not a little more. my boat is a formosa
41 leaky teaky.....teak decks were removed before i could fight them about it.
i wash my cap with sea water
then i oil
it with teak oil finish or tung oil finish whichever i can find. this works well in tropics as i do this once per year day before start of rain season here. lasts me a year.
cetol sukks and i dont sand my teak as green teak is no longer available for use on boats and kiln dried teaK is different than green ....not what you want..
teak oil only blackens if the dirt in the air makes it so and if you allow dirt to build up. wash it with sea water
to clean it and make sure it is clean. then oil it. if there is dirt in the teak the oil will turn black. i use a green 3m pad with sea water only to clean . that is all teak needs.
oh ye- the good part--this process takes me about 6 hours per year.. lol...