TC, the last Merc 1500 was built in 1977. You may have a Merc 115HP motor, which is similar to the 1500, but was built until 1988 or so. You can confirm year by looking up serial number at maxrules.com.
Thanks guys. It must be between a 73 and 77 like you said chris. I am looking at a boat with one of these motors on it. I assumed the motor was the same year as the boat, but I was wrong. That is why I love Iboats, because people on here know what they are doing. Any more advice or opinions would be appreciated.