Will does not call Beanpole and Henry to tell them what he found because he does not trust them.
In chapter 5, Will, Henry, and Beanpole reach an ancient city.
Will remembers the fight with Henry over his father’s Watch. He also realizes that he does not completely trust Beanpole. He talks to Beanpole, and kind of forgot about his struggles with Henry, becoming “complacent.”
So it had happened that I found this shop, with the jewels and the Watches, having left them discussing the strange machine they had found … No, I was not going to call them. (ch 5, p. 90)
Will does not feel a close connection to Henry and Beanpole, and they do not even seem to realize what has happened. He sees no need to tell them about the watch when he is wary of them, and cannot trust them.