You really could be struggling to find an exact match.....Also, is it ply or teak? Even timbers on same production could vary in tone etc. After all it's timber and not consistent. If it's an older yacht it also could have been refurbished at some point. You may be lucky, but realistically your best option is just to mach as closely as possible. Does it really need to match exactly?
Or, depending on where you are replacing the teak, use a different material. My material of choice for all refurbishment is lamipanel. Light and bright and watertight, easy to wipe down, ultra practical and attractive.
I always find it helps to look at the area to be refurbished for a few days and have a think about what will look nice in replacement, and what is practical and updates the appearance. What looked great 30 years ago may not be great now, and materials progress.
My upgrade pics are in an album on my profile, I think people can look at them. You will see the lamipanel. I am replacing most of the old veneer that looked great in the day, but is way too dark, the lamipanel brightens the entire yacht. The roof was tired old vinyl and is much improved with a practical surface. So if you can use something new and different, you may well not need to worry about matching stains.