TOPIC: Lower Unit for a '63 Merc 850

It looks like I am probably looking for a lower unit for my 850. I am having the same problems as the one in the post about cable adjustments. I would like to update to a unit with stainless shafts to avoid problems in the future.
Now my question: what will fit! Other posts I have seen seem to say that most any year will fit, as long as it is from a stack. Anyone with specifics please let me know. Also, anyone that would be willing to part with one, I am interested.
The serial number is 1567648.
Thanks everyone, this a great site!!!
Bill

most to 1964 full gear shift will fit 1965 and latter wont

Take L/U apart and rebuild it, I believe theres a thin aftermarket SS sleave that fits over the shaft to give a perfect seal and wont rust, saw it but dont remember where or what its called.

ADDED: thanks for the product name Thom, ; 'speedi-sleeve' I knew it but been so long forgot.

G3Bill is correct,...The rusted seal areas of both your drive shaft & prop shaft can usually be repaired with a 'speedi-sleeve' from SKF via NAPA.
Armed with the shaft size in question, most old steel shafts can be repaired with these cool little stainless steel sleeves.
I can go into detail if requested.
The reason Dave Bernard limits which era lower units will directly interchange is because of different Reverse Lock Cam designs found on the later model lower units, and the factoid that the later units have above water exhaust reliefs that your original doesn't and can definitely cause a louder 'on plane' exhaust unless you take the time to seal off these 'vents'. It is very easy to do.
The required alteration to the Reverse Lock Cams is a bit more complicated, but I've done it 'more than a few times' for guys.
This & the issue of lower shift shaft length can be over-come though and will result in a no hassle - all stainless shafts lower unit.
If you are interested in having one of us repair your original lower unit in such a manner - there are several on the forum that are more than qualified to accomplish this for you (including me - this winter).
The issue of your being unable to have a good Reverse is easily remedied during a complete L/U tear-down,...IF you want to stick with your original lower unit. Myself & others here can provide the components needed to have a good Reverse if you select to stick with your original lower unit.
I'm located in the state of Washington and can be contacted directly if needed through the fiberglassics contact info.
I can most likely provide contact info to others closer to you if requested.
"Keepin' 'em alive Since 1965"
Doc Frankenmerc

I have the older style 2 piston PT&T, so is the reverse lock cam even needed? I think I could handle the sealing of the vents.
Bill

You are correct. With the '70s style (4) hose (2) ram power trim, you simply disable the reverse lock hooks assembly by removing the push rod going from the hooks to the bronze reverse lock lever and no need to worry about the lock down system.
I believe that you will need to shorten the lower shift shaft in the later lower unit & you may want to use your original aluminum top water pump housing rather than the later plastic housing since you don't have an exhaust tube, but I'm not sure if the plastic pump housing would distort - melt or not since the exhaust does have water in it.
Anybody know???
Thom

Can the shift shaft be changed without tearing down the lower unit? I am assuming the water pump housing will match up? And next, does anyone have a unit they would part with for a decent price?
Thanks,
Bill

Yes it can, just pull it up straight in forward gear without disturbing the shafts or tipping the lower unit and it will swap right out.

I must confess that I bow to George as one of my preferred Mercury Gurus, but a critical detail that would be assumed by a tech is that you need to have the driveshaft pointing directly vertical (commonly with the lower unit secured in a vise) to be successful.
The least bit of angle to perfectly vertical can result is the shift cam siding out of alignment while one shift shaft is out and preparing to put in the replacement.
I also find it VERY helpful to remove the shift shaft bushing assembly prior to attempting R&R'g of the shift shaft.
Doc

also drain and wash the oil out helps to keep it in place.put in foward so there is no spring pressure on the cam.

Thanks everyone for all of the help, but I still need a unit to work on!
This site is great!!!
Bill

I must be dense? Dont say it Thom
Why are you so intent on not repairing yours if most of the parts are good, or is it junk? Would be nice if there were pics??? maybe i'm down to one brain cell .......////,,,,,,,,,,

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All Dunn Bill,
Please write to me and we'll sort this out.
doc_f at comcast dot net
Thom

When at all possible, I like to K.I.S.S. (Keep It Simple Stupid). I just thought that since I have never torn apart a lower unit and had to put it back together and have it work, it would be simpler to pull the old one off and bolt on the new. Then I could tear into the old one and learn more about how they go back together.
I wish I lived closer to some of you guys like Doc, so I could come over and help you guys and learn from the masters.
Doc, I will be sending you an e-mail.
Thanks,
Bill

All Dunn II wrote:

When at all possible, I like to K.I.S.S. (Keep It Simple Stupid). I just thought that since I have never torn apart a lower unit and had to put it back together and have it work, it would be simpler to pull the old one off and bolt on the new. Then I could tear into the old one and learn more about how they go back together.
I wish I lived closer to some of you guys like Doc, so I could come over and help you guys and learn from the masters.
Doc, I will be sending you an e-mail.
Thanks,
Bill

You didn't sound like you need to keep it simple and guess I/we thought you knew more than maybe you do about repairs? Wish more people would explain skils in there first post so everyone knows where there coming from, wont happen though? Think you have a good plan and can always use the old lower as a back-up or sell it? I agree about living near someone like Thom or another big gun and there's more than a few. I should be going up north in a few months but wont have the time to get as far as Thom's place, that really bugs me! Maybe one day? Good Luck on finding a LU...

Today I pulled the lower on my 1958 mark 78 mercury as I was getting water In lower gear oil tried to get water pump housing out to get to seal an bearing tried heat an slide hammer. But no go any suggestions. Also where can I get seal an bearing. Any impute would be nice. Hotrod

This may or may not help, mine is newer, a 1964 65 hp. To remove the lower impeller housing on mine you need to first remove the large flush fitting screw from the side of the gearcase. It screws right into the side of the impeller housing. Hope this helps.

much different. one is full gear shift one is direct reversing.

g3bill,
I understand where you are coming from. I have been a shade tree mechanic for about 40 years when it comes to cars, but have always stayed away from transmissions. I have been working on outboards and small engines for almost as long, but have stayed away from lower units. I guess I am just intimidated by gears, even though I have been accused of being a gearhead!!
Bill

Can I call you Gear Head, lol. Sounds like you have some of the same skils as I do. I had rebuilt VW & Porsche motors but like you stayed away from trans work. Three years ago My 82 toyota truck trans syncros died, thought I'd remove it and send it in but being low on funds I took as much as I could apart but got stuck pulling the bearing to find ya need a hydrolic puller so had the shop put syncros and bearings in and did the rest myself and saved. Also replaced seals on the transfer. later had to rework the rear end, never tried any of this before but did everything except one bearing I needed help with. I set up the ring and pinion with .005 backlash and thats real good, when done was like new and quiet without leaks. Actually I had the shop set up the backlash and was way off so did it myself, cant trust so called pro shops...Also the shop wanted to leave the small end pinion bearing spinning on the shaft which had started to wear, so I found a Loctite that was so strong you need heat and a press to remove it, worked great but has a very short shelf life and assembly must be quick.

With the Merc motor there are some special tools needed but Thom or someone has the diagram to make your own tools if you ever need to try that.

Bill I suppose this is more than you wanted to know? g3Bill

"you need to have the driveshaft pointing directly vertical (commonly with the lower unit secured in a vise) to be successful.
The least bit of angle to perfectly vertical can result is the shift cam siding out of alignment while one shift shaft is out and preparing to put in the replacement.
I also find it VERY helpful to remove the shift shaft bushing assembly prior to attempting R&R'g of the shift shaft."

This is indeed the case. Thank you Thom!!!