I have a 1972. Sea swirl with a mercruiser 140 sterndrive. I am trying to remove the out drive to find where some water is leaking into boat when motor is up. I tried to loosen the six big bolts that looked like it held it on but when loosened nothing budges at all. thought it would just slide off like a driveline. Guess not. Does anyone know if I am on the right track.