Favorite Answer:140 to 180 over normal is the definition of a wide pulse pressure (you can google that term if you would like) which could be caused by atherosclerosis which is not exactly out of the ordinary for senior citizens. But there are also other factors that can manifest as an elevated SBP. Good for you (& him) for the diet & exercise & BP checks. But hypertension is known as the silent killer for a reason. Blood work would be a great idea to get an idea of your dad's lipid profile, & if way out of parameters, a statin drug is an easy fix. But as I typed, hypertension is called the silent killer for a reason, & regardless of the cause, the quicker it comes down, the better chance of a long to longer life, & there are multiple meds that can achieve that goal.
That was the long answer.
The short answer is: yes, get him in to see a doc.