Re: 1963 mercury 1000 100hp 4 cly water pump change out
I have a 1963 850 Merc inline 6 cylinder that should be the same as yours if the year is correct. Although I thought in 1963 the Merc 1000 was also a inline 6 cylinder. I believe mine also had just the six bolts holding on the lower unit. The one in front on top, the two behind that on top, two on the underside of the ventilation plate, and finally the allen screw that holds the trim tab on. Although you might look up in the trim tab area to see if there is another bolt going up into the driveshaft housing. Its been a few years and I can't remember accuratelly. Corrosion may be holding the drive shaft, shift shaft or the water tube in place. Try shifting gears with the shift lever. Also try to slowly spin the motor over with the manual starter to see if it will jar loose the drive shaft from the powerhead. Just make sure the ignition is off. It's also a good idea to remove the propeller just in case. It might be alot easier if you get someone to help you. I use a rubber mallet to give the lower unit a whack.
I also use a heavy duty rubber bungee to hold the lower unit to the drive shaft housing so it doesn't drop off unexpectadly and break a housing or something. Good luck!!! If you do get it off remember to lubricate the splines on the driveshaft and the shift shaft before reassembly.
