Driveshaft / lower unit question for '82 Mercury 800 (80hp)

[tronglasstron]

I need to replace the lower unit on my 80hp 1982 Mercury 800 ELPT, the one with the blue band.
The part number for the lower unit of my long shaft motor is 1655-733a25. They also sold a short shaft version with 1655-733a23.
I am having trouble finding a lower unit that will fit my long shaft model, but I found some short shaft versions for sale.
Is the only difference between the two the shaft? Could I buy the a23 short shaft version of the lower unit, and then just swap out the drive shaft for the longer one?
Any help would be very much appreciated.

 

[jimmbo]

Swapping a driveshaft will require an almost complete teardown of the case, and possibly will require some shim changes too

 

[Chris1956]

As I understand it, the shortshaft motors were the rare ones. Longshaft (20") were standard. I am surprised you found any shortshaft gearcases.

I have a longshaft gearcase from a '77 inline 6. It should fit your motor, but has the 2::1 gear ratio

 

[racerone]

Your location may have something to do with not being able to find that lower unit.-----Lots around I think.

 

[Faztbullet]

Where ya at?

 

[tronglasstron]

Thanks for the input. I'll just keep looking for the long shaft version then.
I'm in Vermont, not to far from the Canadian border. Where should I look besides Ebay? I only saw one on there for $850, and it's from Canada and looks rough. Another is mislabeled and won't fit.

 

[racerone]

Lots available in Ontario.--------Check on KIJIJI on a regular basis.-----You will find one by launch time.