'57 lower unit rebuild

[robot]

1957 35 javelin (rje-19)

i cooked my clutch dog/forward gear(was 'hit a log") then went to just spins...(reverse still works fine)

I have 2 additional lower units(thank you ebay). and a new impeller (it's off, time to replace)

I need to know:
1. what parts (gaskets.etc) I should purchase before rebuilding the lower unit(replacing the clutch dog and forward gear.) i.e. what are the standard parts that get replaced every time a lower unit gets rebuilt?

2. gotchas I might encounter attempting to tear it apart, and putting things back together

3. shop tricks that I might need when rebuilding this lower unit.

4. is there documentation somewhere that shows which models/years are interchangable? I am trying to build a simple arsenal of the required parts to rebuild this rje-19 from scratch in the event of any failure. most of my lower unit parts are from rde-19s. my understanding is that there is no difference between the models of that year except cosmetics.

5. I would like to validate the compression of the lower unit before I attach it to the existing motor (i've rebuilt the entire top end, no reason for the lower unit to muck up everything I've done up there). I have a compression tester. how do i do a simple compression test of the lower unit?

 

[Paul Moir]

Re: '57 lower unit rebuild

1. Iboats, etc, sell a nifty reseal kit for your lower unit that has all the seals in it. Might as well replace them all while it's apart. You can order them peicemeal from the dealer too. Sierra 18-2686 includes a new spagetti, big O-ring for the rear seal carrier, propshaft seal, driveshaft seal, shift shaft seal, pivot screw o-ring, and a pair of fill/vent screw seals.

2. Later model gearcases have a spring/detent arrangement on the clutch dog. Use it if you've got one. Take the gearcase apart in a pan, especially later ones with individual rollers. Don't mix the skedge halves up. Make sure the exhaust drain is clear.

3. If you've got Seloc, ignore the bit about RTV. Extend the spagetti so it overhangs into the rear seal carrier area by 1/32". Completely coat the flanges with sealant on reassembly as the screws are inboard of the spagetti. Coat the screws with sealant too.

4. Although there are major internal differences over the years, for the most part externally the lower units remained the same and can be swapped as a whole. I belive you could use any 60s era 33 or 28hp gearcase, and even some early 70s 40hp gearcases as long as they're from motors without thermostats (single line water pump).

5. Test at a low pressure - on the order of 5psi. A bicycle pump, gauge capable of reading 5psi, and a tire valve stem carved to fit the oil fill hole is a simple setup.

Hope that helps!

 

[robot]

Re: '57 lower unit rebuild

thanks paul.
the exhaust drain has never been reamed. I assume now is the time to clean this up.

only 5psi? I thought I needed something more?

 

[Paul Moir]

Re: '57 lower unit rebuild

No trouble at all robot. Normal modern gearcases are tested at up to 15psi, but that's really excessive for these ones. Given the rather weak cap seal and how it mates to the rear seal carrier, you really risk blowing it out if you go very high. I remember reading some OMC literature that said to test at 3psi.
They don't hold much of a vacuum either since they've only got single seals on the drive & propshaft.

 

[robot]

Re: '57 lower unit rebuild

ok. so here's question #6

how do i build a little pressure attachment to my compressor to pump only 3 PSI?

 

[itstippy]

Re: '57 lower unit rebuild

You don't. Use a manual bicycle pump (one pump down should be about 3lbs psi) or, if you must, turn the air compresser off and run the tank down until it's almost out of air. That'd be a good time to bleed the air compresser tank, too.

 

[tmcalavy]

Re: '57 lower unit rebuild

Having done a lower unit reseal recently on a 58 Johnson 18 hp, be forewarned...this is very frustrating the first time you do it. By the time you are done however you will have had the pumpkin apart at least three times, so by the end of the process you will know it inside and out. If you are okay with that (the patience needed to work past frustration) you will come out of the ordeal a better and more confident outboard owner. If you have a limited stock of patience, I'd recommended having a local mech do the reseal, or use a used lower unit with good seals and have another resealed by a mech so you have one standing ready when you need it. Not trying to discourage you, just adding some perspective I gained from doing this not too long ago.

 

[Paul Moir]

Re: '57 lower unit rebuild

What specific problems did you run into tmcalavy? Perhaps they will be of some help to robot. The 35hp case is somewhat easier than the 18hp since it doesn't have the bearing indexer, but on the other hand somewhat harder because the shift shaft bushing is less accessable, so more difficult to remove.

 

[tmcalavy]

Re: '57 lower unit rebuild

I don't have a well-equipped shop...that was part of the problem. Literally had to beat the prop shaft and driveshaft seals out...holding my breath and hoping not to damage the case where they fitted in. Also took me awhile to figure out the right way to get the shift mechanism reseated in the bottom of the pumpkin...getting that holding bolt/screw back in took a lot of patience. Then the kit I ordered/bought had two rubber O-rings that didn't fit my LU at all...guess it was a later aftermarket kit made for several models. Also no instructions with it, and the Johnson/Seloc manual for this wasn't all that much help...but better than nothing. Also had some fun with the spaghetti gasket cause the manufacturer/packer tied it in a knot?? So I had to unkink it and apply some light heat/warmth from an old hair dryer to get it straighten out and lay in the groove on the pumpkin. Then it was a real chore getting the LU back on and getting the top of the driveshaft rightly aligned with the powerhead grooves/slots. Then I discovered that the last owner had effectively stripped the threads on the bottom bolt of the shift-shaft connector...so I had to replace the connector. And once I got it all back together and ran it in a barrel, I discovered that the water tube missed the grommet on the water pump...so I had to loosen the LU and reseat the tube in the grommet and the LU with the leg/powerhead. Was a real learning experience...I'll say that. Since then I have located another lower unit (used) with good seals that I can use as a backup if the original starts taking on moisture again. Have also learned since then, from an old Merc engineer, that you can run Lubriplate 105 white engine grease in the LU of outboards of this vintage instead of 80-90 wt. hypoid lube, if and when your seals get iffy. Not a cure, for sure, but merely a stop-gap measure until you can get the seals redone. Like I said in my earlier post...not a job for those short on patience or time, but I'm glad I did it. Now I have a closer bond with the old Johnson and more appreciation for it. That's my story, and I'm stickin to it.

 

[Paul Moir]

Re: '57 lower unit rebuild

Thanks for your comments, tmcalavy. It's easy to get spoilt with a well stocked shop and forget about the troubles you first ran into.

I don't like the lubriplate solution, especially on larger engines. Perhaps it's not so great a problem with the 18hp but with the 35hp if you get the slightest corrosion on the roller & ball bearings, they're done. Never mind the gear tooth and clutch dog forces are much higher on the larger engines. And for that reason too I would avoid it on engines with weaker gearcases, like the 10hp. I would much rather see you just regularly replace the 90w to keep ahead of the water infiltration.


But the driveshaft alignment reminds me, always have a look up the midsection with a flashlight so you can see what the driveshaft has to feed through. I think people end up wasting time trying to feed it up through the exhaust or some such chamber after missing the driveshaft guide half way up the midsection.

 

[tmcalavy]

Re: '57 lower unit rebuild

I'm not making any recommendations about using Lubriplate in a larger outboard, simply addressing the 18 hp I worked on. Just couldn't resist your invite to "share." Doubt seriously that a 35 hp pumpkin is any easier to tear apart and reseal than an 18 hp...just wanted him to know what a chore it really is and that if you don't have the patience, hire it done.

 

[Paul Moir]

Re: '57 lower unit rebuild

I'm buying what you're sellin.