Year of manufacture is irrelevant. There should be a metalized mylar label that has the model and serial. Since you have the serial but not model, I assume you got the serial from a soft plug? You definitely do not have a TLDI, so model options are NS40C, NS40D, or NS40D2. The C is a 2-cylinder, the D/D2 is a 3-cylinder. Never replace just the impeller if a full wp kit is available. There is a complete wp kit for each, but they are unique -- one kit fits the 2-cylinder, another one fits the 3-cylinder. You can call Tohatsu America at 214 420 6440 next week (they are moving the warehouse this week), and they may be able to help you figure approximate date of manufacture from the serial number.
