Merc 200 20hp Drive shaft change

[Mac uk]

Ive just got a 2nd hand lower unit for my merc 200 T/bolt 20hp. Problem is the drive shaft end (crank) is a square end my original one was a spline end. I know Mercury changed the drive ends but from what to what and when. I was told the unit was newer than my 1973 but ive a sneaky sus that its an old unit. Saying that its in good nick. Drive shaft is clean and not much play on the gears. Can I change it for my original one.
thanks

 

[Laddies]

Re: Merc 200 20hp Drive shaft change

Take the lower unit case part numbers, they should be cast into the inside of the casting above the cavitation plate from both units and goto http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=200 and check the bearing and gear part numbers they used at lest 2 different number bearing over the years

 

[8075mercury]

Re: Merc 200 20hp Drive shaft change

I have or have had lower units for 20hp Mercury's from 66 to the end in 1980 and all have splined end fits on the drive shaft that mates up to the splined female on the crank shaft.

Sometimes or eventually the spline wears off and I suspect someone squared off the end and cobbled up a fix of some kind. One sorta fix is to shorten the drive shaft, & square off the end. Find a good spline drive shaft with a bad lower end, cut and square. And then splice with square tubing. I have only heard of this being done, however.

The lower unit casting number for '76 and up is 1627 6006
75 and below to 71 was 1627 4404
70 and below were reverse shifting (to my way of thinking) and will not work on a 73 without some modifications.

Hope this helps.

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Funny you should mention the reversed gear select. I bought a lower unit of ebay and it wont fit, finaly worked out gear shift is oposite to my motor. So ive got 2 lower units, one with duff drive shaft and the other with oposite selecting. . to top it all ive got the sack today. do I strip and install the correct cam from my old unit. or go with the shaft change.

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Funny you should mention the reversed gear select. I bought a lower unit of ebay and it wont fit, finaly worked out gear shift is oposite to my motor. So ive got 2 lower units, one with duff drive shaft and the other with oposite selecting. . to top it all ive got the sack today. do I strip and install the correct cam from my old unit. or go with the shaft change.

Add on: the square drive unit part is 1627 6006 so I now know its 1976+, the drive shaft from a 3rd casing (Starting my own Merc parts store here) is 1627 4404 as is the reversed gear select one.

 

[8075mercury]

Re: Merc 200 20hp Drive shaft change

Sorry, I am getting confused around the inventory.
Is this it?
1. 6006 Lower unit with a square drive shaft
2. 4404 Lower unit with a bad splines (came off the 73 to begin with?)
3. 2964 or 3482 reverse shifting with a good drive shaft???

If so, here if what I think I would do:
*Modifying the reverse shifting involves grinding out the shift cam stop lobe in the casing and reversing the action. Not the best option I think.
*Take the reverse shifting lu drive shaft and install in the 4404. Not a bad choice. Depending on how old your reverse shifting drive shaft is, might be an exact match. Bad part is the reverse shifting drive shaft, if original, is carbon steel, prone to rust and leak. But your original 73 drive shaft was carbon steel too.
*Or, find a stainless drive shaft and install in the 4404 lower unit is the best way and unfortunately means more parts needed.
*And finally, and maybe best of best, get another lu on ebay and sell your inventory as the parts are worth something to somebody.

Hope this helps.

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Hi. it is getting confusing. Anyway the last option would be the best exept while looking for part numbers I noticed a crack in the casing of the 3482. Not to worry though. ive got prop shaft, gears (in good nick), drive & shift shaft, water pump from the 73. Im going to strip the 3482 and place all the parts in the spare casing. If the gears of the 3482 are bad due to a water leak ille use the 73 gears, (Ive had them looked at and told there good to use again). My original 73 lu got cracked when the boat was being moved. Ive got a Seloc book which uses the 20hp as the main disription its like having a mechanic looking over your shoulder so they say. The words Tut Tut will appear in the script. The only thing im concerned about is the shimming. Ive been inching to try it for ages so im going for it, if i get a season out of it im happy. As for the 76+ ille hold on to that for spares and try and get a new drive shaft of S/S.
Thanks guys youve helped, Ille let you know how I get on. Mac

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Hi. it is getting confusing. Anyway the last option would be the best exept while looking for part numbers I noticed a crack in the casing of the 3482. Not to worry though. ive got prop shaft, gears (in good nick), drive & shift shaft, water pump from the 73. Im going to strip the 3482 and place all the parts in the spare casing. If the gears of the 3482 are bad due to a water leak ille use the 73 gears, (Ive had them looked at and told there good to use again). My original 73 lu got cracked when the boat was being moved. Ive got a Seloc book which uses the 20hp as the main disription its like having a mechanic looking over your shoulder so they say. The words Tut Tut will appear in the script. The only thing im concerned about is the shimming. Ive been inching to try it for ages so im going for it, if i get a season out of it im happy. As for the 76+ ille hold on to that for spares and try and get a new drive shaft of S/S.
Thanks guys youve helped, Ille let you know how I get on. Mac

 

[8075mercury]

Re: Merc 200 20hp Drive shaft change

The 3482 may or may not have spiral gears. I would use the spiral gears in the 4404 case or the 6006 case. Good news is you likely have plenty of shims in your total inventory. And I like Seloc too. Good book.

And finally good luck.

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Youre probably right, ille use the 73 gears and stuff. Just needed the cover plate and bearing carrier off the 3482. (Youre going to tell me they wont fit now). Ille end up with loads of parts and no outboard. If it doesnt work out, next seasons boating ille take a few friends with me, it takes a bit to row a 20ft cruiser. Thanks

 

[Mac uk]

Re: Merc 200 20hp Drive shaft change

Its been weaks now and no ones probably reading but an update anyway.
Ive stripped the 3482 and it hasn't got splined gears as you said pitty that they look in good nick and I could of just dropped them in. Ill'e use the 73's gears. Question ?. Ive got to put the bearings from the 3482 gears onto the 73's gears, in the manual it says I can't use the roller bearings again, have I got to replace them or if im carefull removing them can I. Also whats the modern equivalent to the Loctite type "A" mentioned in the Seloc manual.

Had to hacksaw the 3482 case apart to get the bearing carrier and bits out in one piece.
Mac