I just came across a quotation from Adams' autobiography in 1756 where he seemingly notes Mayhew's direct influence on his own unitarianism:
17. Wednesday. A fine morning. Proceeded on my journey towards Braintree. Stopped to see Mr. Haven,1 of Dedham, who told me, very civilly, he supposed I took my faith on trust from Dr. Mayhew, and added, that he believed the doctrine of the satisfaction of Jesus Christ to be essential to Christianity, and that he would not believe this satisfaction unless he believed the Divinity of Christ. Mr. Balch was there too, and observed, that he would not be a Christian if he did not believe the mysteries of the gospel; that he could bear with an Arminian, but when, with Dr. Mayhew, they denied the Divinity and satisfaction of Jesus Christ, he had no more to do with them; that he knew not what to make of Dr. Mayhew’s two discourses upon the expected dissolution of all things. They gave him an idea of a cart whose wheels wanted greasing; it rumbled on in a hoarse, rough manner; there was a good deal of ingenious talk in them, but it was thrown together in a jumbled, confused order. He believed the Doctor wrote them in a great panic. He added further that Arminians, however stiffly they maintain their opinions in health, always, he takes notice, retract when they come to die, and choose to die Calvinists. Set out for Braintree, and arrived about sunset.