1966 650 Lower Unit won't drop off

[Mercproject]

I have spent the last 5 hours trying to get the lower unit (gear housing) to drop off the drive shaft housing assembly - anyone guess what's holding it?
All the nuts (5 in total), and 1 bolt have been removed, there is about a 1/16 separation from the shaft housing so it?s not "stuck" to that.
It is in forward gear, and I did try neutral just in case.
I disconnected the "push rod to reverse" lock that sits just inside the swivel bracket assembly (what a chore that was).
It seems like it is hung up on something, and I do not want to bang, pry or force it in case I am about to break something.
The manual and parts book I have do not seem to offer any clues.
I have checked through other posts and have not been able to find a suggestion (I could have missed it).
Again, a 1966 Mercury 650, 4 cyl, Serial Number 1869630, Canadian
Thanks for any help
Andy K :facepalm:

 

[daveswaves]

Re: 1966 650 Lower Unit won't drop off

It is either hung up on the shift rod or the driveshaft. The older driveshafts were not stainless steel and can become one with the engine crank if corrosion has taken place.

 

[mmf]

Re: 1966 650 Lower Unit won't drop off

If motor has been run in salt or was constantly setting IN freshwater the driveshaft might be stuck in the crankshaft, I have run into this many times. On some I had to destroy the exaust housing (bust it with a hammer, used ones cheaper than a lower unit!) and attach two 1/2" flat steel plates bolted together around the crankshaft, then beat the steel plates with a hammer, it's not good at all on the main bearings in the powerhead either, some came out fairly easy, some I never got apart, thats the importance of removing the lower unit regularly and greasing the driveshaft splines heavily, but not on the driveshaft end. I hope you get it off!

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

Thanks for the quick replies - I appreciate it.
The motor has never been in salt water - but it probably has been years since it has been apart. (I picked it up a couple of years ago)
I never thought of the drive shaft getting stuck (at the top right?).
I don't like the sounds of beating it to near destruction, so I will have to ponder this problem for a while - -
Any other suggestions/ideas are greatly appreciated.
Thanks again,
Andy K

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

How could I maneuver it to come off the shift shaft?, or do you mean rusted on / stuck? I am thinking you mean it is getting caught on something when trying to pull it off - you probably mean it?s rusted on!?

 

[chum1]

Re: 1966 650 Lower Unit won't drop off

If drive is indeed rusted to crank you may try hanging it upside down and let gravity do the work, possibly pry it apart enough and shoot pb blaster on drive shaft and let it run all the way down to crank spline.

 

[mmf]

Re: 1966 650 Lower Unit won't drop off

rusted or corroded on. In desperation I have heard others say they have removed the motor and hung it upside down (tied up by the lower unit) and lift it only a few inches (in case it does come off), but this is a next to last scenereo! with the weight of the powerhead etc, it's possible, you can only try!

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

Chum1 and MMF:
This confirms just what I have been thinking. I can leave it supported, with a couple of the nuts in place, just in case, and spray some Deep Creep, (Sea Foam), my favourite rust buster as best as I can on the shaft.
Do I have reason to be concerned about the spray getting into the rest of the motor area (pardon my ignorance)???
This sounds like a tomorrow project, worked on it enough today.
Thanks for the input.
Andy K

 

[chum1]

Re: 1966 650 Lower Unit won't drop off

I wouldn't go hog wild with the stuff but i wouldn't think it would hurt anything, there are a couple seals that seal the crankshaft so don't just pour it in, maybe a couple shots from a squirt bottle.

 

[1960 Starflite]

Re: 1966 650 Lower Unit won't drop off

I can't add to this other than to ask if the ONE bolt that you removed was UNDER the trim tab? That would be TWO bolts, one to hold the trim tab and ONE under it !

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

1960 Starflite:
That is correct - I didn't mention or include the trim tab bolt because you have to get it off to remove the back nut -
Thanks for checking / mentioning it - I can see how it would get missed -
The lower unit has seperated from the gear housing by about 1/16 to 1/8 inch, and has not yet gone any further.
Thanks again,
AK

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

Chum1:
I gave a couple of shots into the opening with Deep Creep, which is nothing more than Sea Foam in a spray can.
I can only hope some made it past everything to the driveshaft/crank connection.
Thanks again
AK

 

[1960 Starflite]

Re: 1966 650 Lower Unit won't drop off

Haven't tried this as I've not had your problem. Wonder if you crank the engine with the starter while the bolts/nuts are loose. Maybe it will shake the splines loose.

 

[Mercproject]

Re: 1966 650 Lower Unit won't drop off

That is a good idea - but it makes me nervous.....

Thanks for the input, I may try it yet.....
AK

 

[Mercproject]

Re: 1966 650 Lower Unit DID drop off - YEAH

Re: 1966 650 Lower Unit DID drop off - YEAH

After following a combination of the suggestions, I was finally able to pry off the LU. As you know I have been soaking the top of the driveshaft (and anything thing else I could spray) with rust buster, then using 2 screwdrivers as wedges and gently tapping with a hammer, which I did previously to no avail.
I think what made the difference was getting some small metal tubing from a hobby shop, bent the end and used it as a spray nozzle to direct a spray of PB and Deep Creep onto the drive shaft.
BUT, once removed, the driveshaft splines didn't look that rusted, actually, not bad at all, but the shifter splines did ? could this have caused all the trouble?
The only thing I would have changed: I removed the upper mount cover bolts to get access to the drive shaft. Removing the Strap Stop bolt would have given me better access, and easier to put back.
NOW THE QUESTION IS: Where did those two mount cover nuts go? AND do I have to take the drive shaft cover housing off in order to put them back on?
As a side note: Half the lower drive shaft seal is missing -
This whole project was started because I was getting water in the LU
Is it possible that water is leaking past the shifter housing and getting into the LU?
I realize I have covered a lot of material here and asked a few questions.
I may have to ask my new questions in new posts.
THANKS TO EVERYONE FOR YOUR SUGGESTIONS - IT WAS A DEFINITE HELP.
AK

 

[Mercproject]

Re: 1966 650 Lower Unit DID drop off - YEAH

Re: 1966 650 Lower Unit DID drop off - YEAH

Found the two nuts and half driveshaft seal by using a blow gun in the cavity.

Further investigation leads me to suspect the rusted shifter splines hung everything up.