QD 16 lower unit

[sbump52]

I have taken the lower unit apart and have found black discoloration in the lower half. I think it is corrosion. What if anything should I do to either stop the corrosion or cover/seal it? I also want to replace the seal behind the prop and the O ring behind it and also the seal between the halves to keep water out. I knew I had some kind of leak because the lower unit oil would be milky and water would come out when changing the oil. Because of that I was changing the oil about every five times out. I also would like to know how to get the seal out. Is there a trick to getting it out? I also suspect water may be getting in to the lower unit around the shift shaft. How do you get to that O ring? For a 50+ year old motor there wasn't much wear on the gears. The dog is worn a little but that is it. No metal pieces but they have been flushed out pretty regular with the oil changes I have a parts book and have the service manual on CD somewhere but can't locate it. Any help would be appreciated.

 

[jasper60103]

Re: QD 16 lower unit

yea, I'm in the mist of a gearcase seal job too.
And about the same stage as you with everything torn apart,
and trying to figure how to get the shift rod and driveshaft o-rings out without doing too much damage.

Another member gave me this post. It should help you out as well.

http://forums.iboats.com/showthread.php?t=277190
see Posts #6 & 8.

 

[samo_ott]

Re: QD 16 lower unit

6 and 8 are exactly how you get the shifter bushing out. The tool is very easy to make and use.

 

[wbeaton]

Re: QD 16 lower unit

Be very careful when removing the prop and driveshaft seals. You don't want to damage the seat around the seals. Also, clean out all the bolt threads and the spaghetti seal grove and use a good sealer on everything. The proper sealant is Scotch Grip #847 which is what I use, but I have used RTV silicone with good results.

Steve, good to see you back. Does this mean your email is up and running? I sent you something last week, but it bounced back.

 

[sbump52]

Re: QD 16 lower unit

Thanks for the replies. What should I do about the corrosion? Should I leave it alone or put something over it to seal it up?

 

[wbeaton]

Re: QD 16 lower unit

What exactly does it look like? Is it flaky, pitted or just discoloured? If its just a discolouration I wouldn't worry about it. Once the lower unit is full of good clean oil it won't corrode. Remember to change the oil every year. Also, check the oil after the first few uses once the lower unit is resealed to make sure it worked. Sometimes they still leak a bit.

 

[sbump52]

Re: QD 16 lower unit

Well I took it to work today and glass beaded the pitted discoloration. I was going to remove the corrosion and alodine the inside of the lower unit half. After blasting, there is a pin hole in it. The pits were pretty deep. Also looks like the casting is very porous. I wonder if Johnson will warrant the part since the casting is not good? I am going to take it to a prop shop and see if they can weld it up. If not, I may try to use an epoxy on the outside and or look for another part. I called my parts house and they are going to see what is available as far as seals go.

 

[jasper60103]

Re: QD 16 lower unit

Hi, Wayne.
I was hoping you could help me out. I'm working up some confidence to start replace the seals on my gearcase. FYI. '62 johnson 28hp.

The driveshaft seal (which is referred to as a oil retainer in my manual). You mentioned in the other thread to take little bites on the lip of the seal only.
So are you saying I should be able to pry out the oil retainer only, without removing the driveshaft bearing? See attached pic.
I'm hoping to avoid damaging the driveshaft bearing, since a replacement may be hard to find.

jasper

 

[wbeaton]

Re: QD 16 lower unit

Now I understand. Lots of old lower units around especially housings. You can pick up a used housing on eBay, from a free ad over at aomci.org or from a marine slavage yard. I'd suggest placing an ad at aomci.org. Someone will give you a fair deal on one. If you just need the housing it'll be pretty cheap. Cheaper than welding and better in the long run.

 

[jasper60103]

Re: QD 16 lower unit

Wayne, looks like I just missed you. bump.

 

[wbeaton]

Re: QD 16 lower unit

So are you saying I should be able to pry out the oil retainer only, without removing the driveshaft bearing?

Yes.

I should also add that since its a bearing below the oil seal and I assume its a roller bearing (I can't see the diagram you posted and I'm not familiar with that exact lower unit) make sure you don't let any pieces that may break off of the oil seal get stuck to the bearing and forgotten.

 

[sbump52]

Re: QD 16 lower unit

Whoa did I just get hijacked?? So would it be a good idea to try to find a lower half rather than welding it?

 

[samo_ott]

Re: QD 16 lower unit

Personally I'd weld it. Cause I'm cheap and it's easy. I have had luck in the past using an aluminum rod and a propane torch patching up a crack in my lower unit cause it froze on me. But it doesn't hurt to investigate both avenues...

 

[sbump52]

Re: QD 16 lower unit

Welded up the corrosion, got the drive shaft seal out by basically tearing it out. Can't get the shift shaft bushing out. I have ground a drill bit down, but can't seem to get it ground so it will engage the bearing without catching the cast lower unit. Any way haven't had any luck. The shop I went to get my parts says the propshaft seal is no longer available. Got the O ring for the prop shaft but didin't have the propshaft seal and says no one has one. What are the chances I could find one at an auto parts store? The drive shaft seal they sold me doesn't have a "back" on it. You can see the rubber seal and the spring behind it and just a metal case that presses into the housing. Is there supposed to be something behind it to hold the rubber seal? Had to order the impellar kit also. A little discouraged about the shift shaft bushing.

 

[jasper60103]

Re: QD 16 lower unit

yea, I hear those driveshaft seals just tear out like that, not pretty. Also, my driveshaft seal (#12) looks like yours, open in the back and a spring wrap around the rubber. From my manual, it presses in place and sits on top of the bearing assembly (#13). Click on image to enlarge.

 

[wbeaton]

Re: QD 16 lower unit

If you can't tap the shift shaft seal out from below then try tapping threads into the bushing from above, thread a long bolt in it and then carefully pull/pry the bolt out. I find it easiest to place a piece of wood or metal with a hole in it across the top of the lower unit with the bolt and a washer inserted into the middle of it and threaded partly into the bushing. Make sure the bolt is snug against the wood/metal. Then simply thread the bolt further into the bushing by turning the bolt with a wrench. Since the bolt can't go lower it will force the bushing to pull up. You may have to add spacers as the bushing comes up. Don't worry about damaging the bushing with threads. The bushing only holds the o-ring in place. The o-ring does the sealing.

I've just done a search and I've discovered that you are right about he seal being NLA. A few places still claim to have the entire seal kit for that lower unit for a reasonable price, however, I doubt they have many if any. The entire seal kit is much cheaper than buying the seals individually. The part comes up as "vintage special order" for around $30. This means someone still makes it. Take a set of calipers to it and mic the ID and OD. Then search the internet for an oil seal with the same dimensions or go to an automotive seal dealer.

If the new driveshaft seal is only "half" the old seal then what you do is double up the seal. Insert two into the housing. One seal pointing up and the other down. Like this ][.

 

[sbump52]

Re: QD 16 lower unit

Thanks for the tips. The hole for the bushing is also drilled off center. One side of the hole is right next to the side wall. I might go get a long piece of 1/4-28 all thread and a couple of nuts. Thread a nut on the bottom end push it throught the hole, cut a hole in a board that spans the housing, push through the board and tighten a nut on the top until it pulls the bushing out. I will get another drive shaft seal and put them back to back as shown. And start looking for a prop shaft seal.

 

[sbump52]

Re: QD 16 lower unit

Never mind on the all thread through the bushing. The bushing doesn't go all the way through. I will try to thread a bolt into the bushing. But a 1/4 drill passes through the bushing. Guess maybe a metric bolt that is larger than .252?

 

[jasper60103]

Re: QD 16 lower unit

Wayne,
I didn't know about adding two driveshaft seals back-to-back (][). I know my kit only came with one. I assume the idea here is to make it seal better. I'll keep this in mind when I replace mine. I'm not sure I'll have space to press fit two seals in there. I'll see though. Thanks for the tip. jasper

 

[sbump52]

Re: QD 16 lower unit

Well I got the bushing out, but at the cost of a crack in the side of the lower unit side wall. I went and purchased a spade bit like someone had shown using. I used a deep socket over the blade and the socket was too big around. I had just about reached the point of frustration and didn't pay enough attention. I saw the bushing start to come out, but didn't check for clearance around the socket. A couple of blows later there's the crack . I will try to get it welded and see if that will hold. I still need a prop shaft also, so I am about to start the search for one of those.