fishsmith; I'm not sure about a serial number on the block, but, find the model and serial number tag on the mouting bracket. Should be a small aluminum tag on the left side of the motor when looking at the stern of the boat. A 1993 Johnson 150 will have a model number something like; J150TXET
The "J" for Johnson; 150 hp; "T" for power tilt/trim with electric start; "X" for 25" shaft length; "ET" for model year 1993.
Hope that helps.
