85hp Force lower unit disassembly? Stuck driveshaft...

[62Scout]

Picked up a boat over the weekend with an 85HP Force with a frozen lower unit. Was going to just swap over the motor from my other boat, but figured I might as well see what's wrong with this one first. Would seem silly to do a motor swap if it ends up just needing a couple bearings and seals.

Found zero oil, and about a 1/2 quart of water when I drained it. Pulled the lower unit, found the driveshaft stuck. Prop spins in neutral, but the bearings are obviously shot.

Pulled the impeller housing and lower plate, and the prop, and I'm not seeing any obvious method of getting the lower driveshaft out.

Behind the prop, there's a notched ring with "off -->" on it, which I assume means it is threaded in, but I couldn't get it loose with a drift and hammer. Special socket needed?

 

[The Force power]

Picked up a boat over the weekend with an 85HP Force with a frozen lower unit. Was going to just swap over the motor from my other boat, but figured I might as well see what's wrong with this one first. Would seem silly to do a motor swap if it ends up just needing a couple bearings and seals.

Found zero oil, and about a 1/2 quart of water when I drained it. Pulled the lower unit, found the driveshaft stuck. Prop spins in neutral, but the bearings are obviously shot.

Pulled the impeller housing and lower plate, and the prop, and I'm not seeing any obvious method of getting the lower driveshaft out.

Behind the prop, there's a notched ring with "off -->" on it, which I assume means it is threaded in, but I couldn't get it loose with a drift and hammer. Special socket needed?
View attachment 389912View attachment 389913View attachment 389914

Yeah...that is the Merc "updated" LU
That tool is called a spanner tool (I made my own a view years ago) that tool may not be necessary if you pre-soak with WD40 heat & patience unless its a saltwater, then you'll have to; just break it away. but I don't see any corrosion built up. good luck on the rest of it in there

 

[62Scout]

Yeah...that is the Merc "updated" LU
That tool is called a spanner tool (I made my own a view years ago) that tool may not be necessary if you pre-soak with WD40 heat & patience unless its a saltwater, then you'll have to; just break it away. but I don't see any corrosion built up. good luck on the rest of it in there

As far as I can tell, this motor has never seen salt, but of course it's hard to say for sure on anything that's 30+ years old.

I googled the tool, and it looks an awful lot like a 4WD axle nut spanner...but of course I don't have any axle sockets that big,nor do I have any steel stock large enough to make one on hand. Looks like I can buy a cheap imported version for $40 on our favorite Chicom imported junk site, so I'll just do that.

Thanks!

 

[Nordin]

As The Force power says, penetrate with penetrating oil heat up the gear housing with a torch or acetylen/oxygen welder torch.
Use a drifter and a hammer try to unscrew it.
I have made a tool similar to the factory tool from a piece of steel tube then I have welded heels/tooth at the outside rim of the tube that fits the notches in the nut.
Important that the pattern of the tooth/heels fits snug in the notches.
Then I have welded a tube and a nut to this piece of tube with the tooth tha fits a 3/4 (19 millimeter) socket wrench.
If you do not get i loose you have to drill some holes in the nut and crack it loose.
Try to get it loose by the tool or a drifter and hammer.
A new nut is expensive about 65 dollars if you can find one.
Looks like it is N/A at Mercury dealers.

 

[jerryjerry05]

at least 2 Special tools.
Not a lower unit for an 85hp.
94 to 99 Force lower.

 

[The Force power]

at least 2 Special tools.
Not a lower unit for an 85hp.
94 to 99 Force lower.

Likely swapped out they both (2 piece shaft)
I'm more worried about the internal-guts judging by the upper shaft-bearing

 

[The Force power]

As far as I can tell, this motor has never seen salt, but of course it's hard to say for sure on anything that's 30+ years old.

I googled the tool, and it looks an awful lot like a 4WD axle nut spanner...but of course I don't have any axle sockets that big,nor do I have any steel stock large enough to make one on hand. Looks like I can buy a cheap imported version for $40 on our favorite Chicom imported junk site, so I'll just do that.

Thanks!

I would just try with WD40/heat/patience first, I have seen lots far worse than that & got them out.
Helpful tip; when tapping the ring, alternate/switch positions so you don't stress one tooth only.
after removal clean the treads with a wire-wheel thoroughly!
Make sure the locking-tap is bent open so it can turn ( or is that just on the Mercs? can't remember)

 

[The Force power]

I have made a tool similar to the factory tool from a piece of steel tube then I have welded heels/tooth at the outside rim of the tube that fits the notches in the nut.
Then I have welded a tube and a nut to this piece of tube with the tooth that fits a 3/4 (19 millimeter) socket wrench.

Mine was a tool I originally made for removal of the hub/pulley for replacing on a Subaru main-crank pulley.
I welded multiple bolts on a steel washer (donut size) and a pipe for leverage
After I converted it to fit the spanner-nut.

 

[62Scout]

Maybe the LU has been swapped...I don't know. Like I said earlier, can't really know for sure on something that's decades old and has had an unknown number of goober hands on it, lol.

The powerhead looks virtually identical to my other 3 cylinder Force 85, and that one has the expected one piece driveshaft, along with a slightly difference impeller housing...which was just enough to keep me from simply swapping lower units.

I bought this boat only for the hull, which I had planned to swap my good motor over to, and got it cheap enough that I consider the "bad" motor to have been a free bonus. So even if I toss a couple hundred of tools and parts at it, I still see it as a deal. Either I sell it at that point, and bring the cost of the hull closer to free, or I have a good spare motor on hand for cheap.

As it turned out though, I may still end up having to make a tool for the prop carrier bearing anyways...the one I got from Amazon ended up being about 1/2" too large in diameter to fit. I see $40 as cheap enough to not be worth my time to make something, and if it involves expensive nuts to replace, I'd rather just spend the money to buy the correct tools than chance goobering up the nut with a hammer and drift (FAR too many hours spent digging out 4x4 axle bearing nuts that were destroyed by dipschmits with a hammer and chisel).