To the bottom of the Lark

[Cadillac-ack-ack]

First off, let me say with the suggestions from other about what should be replaced (all the bearings I was questioning about re-using or replacing were replaced) and with a Seloc manual, the power head is finished. New pistons, rings, all bearings seals and gaskets. A nice hone job and she turns freely with just the right amount of that "new engine piston drag".

The waterpump is next and I've got a couple of related lower unit questions. To re-state a little history from my very first intro. This engine was dads and had not run for a lot of years. Around 15 years ago I changed the impeller and changed the gear oil, fired it up and ran it on the lake just two or three times. As I recall that initial draining was a bit milky. Fast forward to now and the gear oil that came out was pretty much just oil. A bit dark grayish with slight traces of tan. I don't know if I should let sleeping dogs lie or attempt to get the lower housing off the upper part and re-seal. The same goes for the bearing head seal. That piece is pretty corroded an I don't want to get to the eve of destruction getting it off if not needed. The water pump seal will be replaced. Am I right in thinking these three places are the only areas water can get into the gearbox? And I'm wondering, since this motor has been stored on a stand for the past 15 years, would not gear oil leak out if there was a bad seal or joint? There is not even a stain or a hint of oil at either the bearing hub seal or the parting joint for the lower housing. - Pete

 

[jimmbo]

Places where oil can get out and water getting in are Propshaft seal, driveshaft seal, shiftshaft seal, spaghetti seal on the gearcase housing split, O-ring on the back bearing carrier,, gasket on shiftshaft pivot screw, and of course the two seals on the drain/vent screws. My dads 1957 35hp had a porous casting and seeped oil making blisters in the paint. Some leaks only happen when running, as when water, under pressure from the pump overcomes the seal below it, oil is then pushed out another less than perfect seal and may not leave any evidence on the garage floor.
Was there any shiny metalicness to the oil? I would change the oil again and keep an eye on it.

 

[racerone]

Let me think here.----Shift rod seal / driveshaft seal / propshaft seal / o-ring on propshaft seal housing / fill and drain plug seals / " spaghetti seal " on the half joint.----When a motor is running pressure builds up on the oil and leaks may occur.----All this work on the power head and now you are scared of opening the simple gear box ??

 

[F_R]

Is that an electric shift Lark? A very different critter from the manual shift ones.

 

[Cadillac-ack-ack]

Is that an electric shift Lark? A very different critter from the manual shift ones.

Yes it is electric, so, no shiftshaft seal, no spaghetti seal. The fill/drain screws I didn't mention but am aware. Racer mentioned the prop shaft seal, that's the one I'm calling the bearing head seal (from my book). And I am looking at the shaft seal located in the top of the lower unit housing, I missed that one. The housing is not off yet but looking down the driveshaft tunnel shows neither water or oil has ever been there. So,,, Lower gear box housing - to - housing joint, Bearing head seal, Water pump seal, Drive shaft seal at top of housing, and of course the screw seals. That looks like the whole package for a leak free gear box. Is this about it?
Racer, I'm not a-skeerd of taking it apart, but because of the corrosion around that bearing head and related erosion of it's seal area I'm concerned with that expensive piece breaking up around the seal area. And if it ain't leaking.... Same with the parting joint between gear case and housing along with those long, perhaps frozen studs. There is apparently no spaghetti seal or gasket there, just machined flanges that need sealer. - Pete

 

[racerone]

There is an o-ring seal between the lower and upper parts of the gear housing.

 

[Cadillac-ack-ack]

There is an o-ring seal between the lower and upper parts of the gear housing.

OK, I see that one now too.

 

[F_R]

If it is working ok, I would avoid taking it completely apart. The prop shaft seal/bearing head should come out with no big problem. Same with drive shaft seal.

Bigger question: How is the electrical cable that leads down to the gearcase? Many/most of them are rotted and NLA. And that is a dis-assembly project if it needs replacement and can find one. If you do go there, be aware that an awful lot of people have destroyed the forward and reverse coil leads by yanking them in two while separating the cases.

EDIT: I get mixed up in my mind over the differences between the 40 and 75hp electric shift lowers. I guess that's why they make parts books. OK, looking at the book now, I see that the 40 does not have a removable seal housing on the drive shaft, so that means take it apart or just dig it out. I dig 'em out. Also, it appears the prop shaft seal goes in the bearing head from the outside, so that can be dug out also---but it's easy to pull the bearing head instead. SOME prop shaft seals (75hp ??) go in from the inside, requiring pulling the gearcase head and then removing the needle bearing from it in order to get the seal out. That destroys the needle bearing if done according to the book with special tool.

 

[Mohawkmtrs]

Haven't worked on a Lark (or any elec. shift) but cannot the gearcase be pressure/vacuum tested first?

 

[racerone]

That would be a logical first step.---Worn seals may still test good as the pressure holds them against the shafts.----Used parts are readily available in many areas were electric shift is not frowned upon !

 

[Cadillac-ack-ack]

Thank's F_R, The portion of the shift cable I can see before it goes into the grommet and disappears in the lower unit looks fine. In there is where it can get tender? Bearing heads including a new seal are ebay available for good prices. I think that's the way I'd go if I decide on seals because the seal recess on the one I have has lost enough material do to corrosion that I think it could break up when digging the old seal out, or the new in. I have a P/N of 0378526 for that, sound right for a '62? There is some very fine metallic haze in the oil, about what you would see in fine metallic paint, no chunks. I'm thinking (hoping) it's normal do to the repeated locking up spring system of the Selectric gearbox. The metallic haze is weekly magnetic. With a magnet it can be dragged around in solvent thinned oil but does not pull up and fuzz up the magnet so I'm pretty sure it's not from gears or bearings. Would it be a good Idea to flush this? I was thinking WD-40 would move some old oil through but still not dry out the parts.
I have a gear oil type question related to the first time I drained and re-filled the gearbox. The oil that came out 15 years ago was white lithium grease color. I thought it may have been contaminated with water but now I'm thinking that was the color of the oil when it went in. Was any gear oil brand from 25-30 years ago white? The oil I replaced it with 15 years ago is correct for Selectric shift gears and came out still looking like oil. - Pete

 

[Cadillac-ack-ack]

That would be a logical first step.---Worn seals may still test good as the pressure holds them against the shafts.----Used parts are readily available in many areas were electric shift is not frowned upon !

Damn. I type so slow! My last post did not address pressure testing because the posts for this idea were not there when I started a finally finished my last one. How much pressure are we looking at for testing? - Pete

 

[jimmbo]

Back in the day the oil speced was "Type C". BRP presently markets it as Precision Blend. There are aftermarket brands of Type C, however some are not Electric Shift compatible. As for White Lithium Grease, that would be bad in that unit. It was probably water contaminated oil. That unit does not use a magnet on the drain plug, so any fine particles are free to go everywhere. If you want to flush the unit, ATF is often used. Pressure and Vacuum testing is a good plan, but as racer pointed out it is not perfect.
Since you are putting/have put a bit of time already into the motor, a reseal and inspection of the internals of the gearcase might not be a bad idea. One thing is to use new self locking nuts on the two studs that hold the upper and lower section together. I know some people reuse them but...

 

[F_R]

Confirming, 378526 gearcase head assy. If the rubber covering on the shift cable is not all dry-rotted, you got lucky there.

 

[racerone]

The metallic bits in the oil are a huge concern !----Take the unit apart for inspection now.----Be a shame to waste nice summer days working on that..

 

[Cadillac-ack-ack]

Back in the day the oil speced was "Type C". BRP presently markets it as Precision Blend. There are aftermarket brands of Type C, however some are not Electric Shift compatible. As for White Lithium Grease, that would be bad in that unit. It was probably water contaminated oil. That unit does not use a magnet on the drain plug, so any fine particles are free to go everywhere. If you want to flush the unit, ATF is often used. Pressure and Vacuum testing is a good plan, but as racer pointed out it is not perfect.
Since you are putting/have put a bit of time already into the motor, a reseal and inspection of the internals of the gearcase might not be a bad idea. One thing is to use new self locking nuts on the two studs that hold the upper and lower section together. I know some people reuse them but...

The "white lithium grease" remark was a color description of the oil I drained, it was not actually grease. And since no one confirmed that there was a white gearcase oil ever offered I'm coming to the conclusion that the white stuff was indeed water contaminated oil. So,,,I am leaning to replacing all the seals, but I won't be getting into the gearcase proper. I'll be happy if (a) the prop shaft bearing hub comes off, and (b) the gearcase can be separated from the housing without destroying the wires and I admit I am a little paranoid that those two long studs will be frozen in the housing. The Seloc book scared me a bit about this. - Pete

 

[Cadillac-ack-ack]

The metallic bits in the oil are a huge concern !----Take the unit apart for inspection now.----Be a shame to waste nice summer days working on that..

I here what you're saying and I agree it's not good to see this, but I really think it's a more a by-product of 20 years of hard use rather than components on the brink of disaster (I know the motor is 56 years old but the first 20 saw the hardest use as an almost constant summer vacation water ski hack). Those shift springs locking, releasing, locking, releasing again and again must account for some normal wear. Again, this is more of a metallic sheen, can't even really call it "bits". - Pete

 

[racerone]

Oh well , I have worked on one or more of these units.----I consider them easy to work on.---Others will argue that !

 

[jimmbo]

Oh well , I have worked on one or more of these units.----I consider them easy to work on.---Others will argue that !

I agree they aren't too hard to work on,but a bit different from the OMC mechanical shifters of the time, and I guess that spooks people, until they take one apart

 

[racerone]

I believe it is the word " electric " that is the problem.---Parts and pieces are easy to work on.