A Model # would come in handy to determine what year it is as OMC engines didn't have a tel-tale until the very late 1970s. If your motor has one, there will be a water discharge nipple on the cowl pan
It won't have a tel-tale. It does have a Horn in the control box that is supposed to go off when the Engine overheats. Some Water is discharged thru the Idle Reliefs( 2 round holes a bout 4 inches below the cowl pan)
Just install a new impeller if you do not know how old it is.------Test your hot horn.------You do not need a tell tale.-----Have seen many motors start with a " slow to pee " tell tale.-----Owners still go out on the lake.------They do not know what how to interpret the tell tale.-----And a water pressure gauge is also a good investment and better than a tell tale.
