War with lower unit

[Yesterday]

I've started attempting a lower unit rebuild on a 1975 Merc 850. I've read a bunch of related threads and was prepared for a struggle with the probability that the drive shaft is corroded to the crank. It came down around 1/4" and then stopped. Using the wedging principal, some elbow grease and some patience, I got it down some and then was able to use a large prybar and work it to the point where I would think it's about ready to drop, and then it stopped moving. I don't recall reading any threads in which they became stubborn again at about the 1.5" point and I'm wondering if anyone's encountered this before? As it stands now I can fit a 2X4 on it's flat side, in either front or rear gaps between gear casing and the middle unit with perhaps 1/8" to spare, but it doesn't want to move any further. There was no "snap" and suddenly it's free either which concerns me some. That said, nothing sounded or felt like it broke off. Any hints or suggestions would be greatly appreciated.

 

[emckelvy]

Re: War with lower unit

The driveshaft should be already released, the lower unit having dropped that far already. How 'bout the shift shaft, can you see the splined end of the shaft or is it pulling out of the lower unit. Common problem if the coupler at the end of the upper shift rod has frozen to the lower unit's shift shaft. Don't despair if the shaft pulls out of the lower unit, there's a way to reinstall it without full disassembly of the gearcase, we'll cover that later if necessary.

Another place it can hang up is the exhaust tube, which slips into a rubber gasket, in the rear recess of the gearcase. If there's a lot of corrosion the exhaust tube can lock in place and make it extremely difficult to pull the lower unit down.

About the only other thing left to hang up is the water tube, and it should have pulled out of one end or the other by now.

Try wiggling the lower unit, at front and then at the rear. See if you can tell what's hanging up. A good spray of penetrant may help. And you may need to apply heat to help release the parts. Be sure to have a fire extinguisher handy if you're using a torch!

At this point you should be able to use some plastic, wood or metal wedges (woodcutting wedges should work), and continue to wedge the gearcase from the mid-section. Just keep an eye on where it's hanging up, and hopefully you can get 'er down.

HTH & let us know what happens.........ed

 

[Yesterday]

Re: War with lower unit

I'll have a look at that shift shaft in the morning Ed, thanks!
How confident are you that the drive shaft is out at that distance?

 

[Yesterday]

Re: War with lower unit

BTW I noticed the exhaust can is pulling up on the rubber gasket but I can work that back into place fairly easily.

I have to pull the carrier out to get at it's O-ring so I ill be inside of the gear case shortly, regardless.

 

[Bosunsmate]

Re: War with lower unit

I agree with emckelvey, the shift shaft splines seize into the upper portion (the female part).
The drive shaft would of being the first thing to move and since it has moved it wont be your problem.
You could try undoing the top of the shiftshaft in the cowling but those are normally seized in there too.

 

[Moody Blue]

Re: War with lower unit

Are all of the LU studs now clear of the driveshaft housing? Possible that one of the studs is badly corroded and hung up in the hole that it has to pass thru.

 

[Maxz695]

Re: War with lower unit

I say shove it back up and use some lube. keep working it it will come in time. If the motor is not on the boat tip it upside down to get the lube in the midsection to where you need to have it. Or Hang it(the motor Upside down) but put something under it as not to cause damage when ti it when it falls. JMO

 

[emckelvy]

Re: War with lower unit

Are all of the LU studs now clear of the driveshaft housing? Possible that one of the studs is badly corroded and hung up in the hole that it has to pass thru.

Yeah, that's a good point, I've had the stud in the very front of the gearcase get stuck pretty bad into the mid with salt deposits, and had to heat the heck out of it then douse with penetrating oil.

 

[Yesterday]

Re: War with lower unit

Yeah, that's a good point, I've had the stud in the very front of the gearcase get stuck pretty bad into the mid with salt deposits, and had to heat the heck out of it then douse with penetrating oil.

The studs are all clear, in fact they're surprisingly free of any corrosion. It's definitely hanging by something in the front interior, and hopefully I'll be able to figure out what, very shortly. It's on a home made stand and not on the boat, and though inverting it would be a huge pain in the ***, it is doable.

 

[carholme]

Re: War with lower unit

Here is the parts list for that engine.

http://www.crowleymarine.com/mercury-outboard/475.cfm

If you look under BOTTOM COWL AND SHIFT LINKAGE, you will see the upper shift rod, item 16 and the coupler, item 17, which connect to the lower shift shaft, item 41 under GEAR HOUSING ASSEMBLY, COMPLETE (PAGE 1).

With the studs clear, can you see the base of the shift cam, item 48 under GEAR HOUSING ASSEMBLY, COMPLETE (PAGE 1)? If you haven't seen the shift cam before, scroll down to item 48 and to enlarge it, click on the picture and click it again when the new window opens.

As well to see if the coupler is still engaged, try to shift the boat controls into forward or neutral and see if the prop responds.

Forward gear: Prop will ratchet when turned CW and will not turn (except for the amount of gear mesh) when rotated CCW
Neutral gear: Prop will turn freely in either direction
Reverse gear: Prop will not turn in either direction (except for the amount of gear mesh)

Gerry

 

[Yesterday]

Re: War with lower unit

Carlholme:
If I'm not mistaken, the shift cam you refer to is a plastic piece? If so then Yes I can see it and it's in somewhat of a free float. Perhaps sliding loosely up and down one shaft. I remember noting to myself to be careful with this lobed piece of plastic last evening. The prop actions you mention were for sure the case before this surgery started yesterday. I will check this today as well!

 

[Yesterday]

Re: War with lower unit

OK so although I'm not %100 certain what I'm seeing here, it appears as though the shift shaft is indeed seized up hard. There is a lot of spline beneath the coupling which makes me think I've not yet pulled it up through, but I'm not certain. Heres a couple of pics which might help assess.

I've tried using a 4 ft 1" think pry bar and I reckon I've applied about 160 lbs to the end of it while blocking up the backside and it didn't budge. It was to the point that I wasn't comfortable putting any more pressure on it. I have since coated the shaft with seafoam penetrating lube but in it's current position gravity is not going to help much and I doubt it climbs up hill, so an inversion might be necessary. As for applying heat, all I have access to is a hand held propane torch, and I worry I may melt that plastic part. (shifting cam??)

 

[Yesterday]

Re: War with lower unit

Also got to thinking with some help from a friend, judging by the rust on that shaft, would I not have to replace it? I'd suspect it will probably mangle a new seal even once cleaned up on a wire wheel?

 

[carholme]

Re: War with lower unit

I just had a look through your previous posts and see the s/n 7071854. Is this the s/n of this engine? If so, that is a 1976 model, Canadian built engine. The previous parts list was for a 1975 as listed in your first post. I have edited the parts list in my previous post to reflect the correct parts page.

I notice that you appear to have the older two piece metal cam, not the newer composite one, so you won't hurt that with heat but you may hit the guide buried up in the base of the driveshaft housing.

Here is a link to the condensed version of the Clymer manual and if you look on page 287, figure M12-63, you will see the two part cam and below it, the newer style.

http://web.ebscohost.com/serrc/pdfv...9377-b9675a3c1e5a@sessionmgr114&vid=2&hid=128

Download soonest to your computer as the link is short lived.

Gerry

 

[Moody Blue]

Re: War with lower unit

A few thoughts on your situation.

1) That shift shaft is toast. I have a couple laying around that I can send you if interested for the cost of shipping. Let me know.

2) Don't pry too hard or you may bend the linkage arm up at the powerhead or pull the shift shaft out of the lower unit by breaking the retainer clip. That could mean disassembly of the lower unit to retrieve the broken clip.

3) that front stud (forward of the hammer handle) is not fully thru the exhaust housing hole. I have had one LU get hung up there.

4) the gold colored sleeve visible in photo 2 is splined at both ends. I would think that one end or the other would have pulled free by now. Double check that front stud.

 

[Bosunsmate]

Re: War with lower unit

Your reverse locking cam has for some reason slipped down (photo one) it should be kept on the uppersleeve in the midsection. So you can heat away on the sleeeve in photo2 and see if that breaks it free eventually. The reverse cam is pretty tough but they can catch on fire so keep a bit of water ready.
Mine combusted a few times but its still very operable.
I suspect you may end up taking up the spare part offer, as moody blue said you dont want to derange the upper shift linkage arm as fixing that may involve lots of powerhead area disassembly.
Heats what worked on mine and it eventually came out with very clean splines

 

[Yesterday]

Re: War with lower unit

@carlholme:
yes i's a'76 not 75! Not sure what I was thinking when I typed that!!
Which Link?

@Moody Blue
I would certainly appreciate that because I think you're right re: that one being finished.
Funny you mentioned that front most stud. I was eyeballing that a little closer this morning, and even gave it a shot of eafoam "in case". I may try a little persuasion with a center punch on it, in fact I will right now!

 

[Yesterday]

Re: War with lower unit

Update:
I tilted this motor up and wiggled it up & down. It slides (slightly) freely along the front most stud, so it's not hung there. When I lift and drop the LU (an easy 1/4" play) the shifter rod and the collar around it moves with the LU. I heated the collar and allowed it to cool twice, applying pressure while hot and after the fact, and nothing. Again I'm only using a hand held propane torch but it seems to be heating thiings up pretty good and making some smoke of the penetrative oils but to no avail. At this point I'm tempted to toss a metal blade on the sawsall and chop it off?!?! If for sure it's toast, that can be easily done.

Also may be trivial but the part #48 on this link just came out in 2 parts.:
Mercury & Mercruiser Parts, GEAR HOUSING ASSEMBLY, COMPLETE (SERIAL GROUP #1) (PAGE 1), MERC 850

 

[Yesterday]

Re: War with lower unit

Oh, and:
yes the shifter is still causing the gearbox to shift as it should, and the shifter cam is composite, what's left of it anyway.

 

[carholme]

Re: War with lower unit

Edited my post and included the link for the manual.

If it is part 48 that came out in two pieces, that would be the two piece cam.

Gerry