Re: 1971 Thunderbolt 500 Lower Unit Stuck on Exhaust
There are 3 things that connect in that interface. A quick reference is on the right side of this site, at least for the boats, props, and Merc sections, is a picture (advertisement)of a lower unit and it shows the drive shaft and the mounting spot on top of the pump housing where the water tube connects....the water that carries the output of the pump to the bottom of the engine block, and to the left the little short shaft right in front of the lower unit casting which is the shifter splined shaft. For you to be able to drop 5" and then come to an abrupt stop is confusing to me...i.e. what is still connected when you have dropped that far? Only thing I can think of is the shifting mechanism is hanging up.
I think your shifter is like larger engines and the lower unit advertisement on here I mentioned. If the shifter disconnected like I think it is supposed to, then you will have a 3/8 diameter splined shaft sticking up out of the lower unit with the shift rod receptacle (female) disconnected from it and you can look up and into the midsection and see it. The water tube can either remain connected to to the block and separate at the pump, or vice versa.....just ensure that that pipe gets connected on both ends when reassembling.
If you have a solid rod (rather than the splined connector mentioned) then you may have to go up to the top of the shaft and undo a clamp....up under the powerhead. They use the clamp thing on lower hp engines so that is why I don't think yours is like that.
I'm at a loss.
Mark
just finished impeller change on '74 thb 500 exhaust tube could be sticking to gasket in lu should be able to gently work it loose.