1957 evinrude lark seized, damp crank case.

[Jdunham]

Hello,
I picked up a 1957 Evinrude lark (35HP) last month.
It has spent the better part of 40 years in a dirt floor basement, without plugs...
As you might expect, it is stuck solid.
As soon as I got it I pulled the exhaust side covers off and sprayed the cylinders and crank case liberally with penetrating oil.
We are now almost a month on and I decided to take a closer look.
I pulled the head off, and what I saw there wasn't too bad. Lots of carbon and only slight surface rust in one spot on the lower cylinder. No scoring but also no cross hatching.
I pulled the exhaust side covers off again and got a better look with a light. This is where I need some input. Every part of the rods and crank that I can see is brown with surface rust. No flake or pitting visible but definitely rust.
So the question is, do I keep soaking and tapping on the pistons with a block and mallet and hope it breaks free or do I tear it down completely?
What are the chances that the bearings and races are ok or that if there ok now they will be ruined by just trying to get it to turn.
This was a freshwater motor and there is no evidence of overheating.

I would love to be able to share pictures, what is the current favored method with the local image hosting down?

 

[racerone]

take it apart.

 

[jimmbo]

I know you want someone to answer, "Oil it up crank away! It'll be fine" NOT!
You said the Rods and the crank have Rust, that means any oil in there is long gone and the Rod and Crank Bearing surfaces might be just as dry. So do as racer said...

 

[oldboat1]

...if you are sure it's rust. Dirt floor basements are inviting to insects, and mud wasp nests can look like rust -- not that the stuff isn't abrasive on its own. Might spray some WD-40 at a spot or two and see if the brown melts away.

The '57 Lark is a great motor, and worth restoring imo -- and might already be in decent cosmetic condition under 40 years of dust.

 

[GA_Boater]

Take it apart - Even oil doesn't last 4 decades.

I would love to be able to share pictures, what is the current favored method with the local image hosting down?

Use Option 2 to upload from your computer - Photo Tutorial

 

[oldboat1]

I've gotten used to using the attachment method (option 2 of the tutorial). Put a folder for pics on your desktop so you can easily locate what you want. If you want to imbed a photo, use the smaller size (tutorial uses a big one).

 

[GA_Boater]

I've gotten used to using the attachment method (option 2 of the tutorial). Put a folder for pics on your desktop so you can easily locate what you want. If you want to imbed a photo, use the smaller size (tutorial uses a big one).

Option 2 tutotial shows where to select Thumbnail, Small, Medium, Large or Full Size. If detail is needed, don't use an itty bitty pic.

 

[oldboat1]

^^agree.

 

[F_R]

Even if you do manage to break it free, it probably is junk. The ONLY way you can tell is to take it apart and examine the bearings. If they are rusted and pitted, and you start it up, it won't last very long before going boom.

 

[Jdunham]

Thanks.
Deep down I knew I needed to take it apart, I just didnt want to admit it yet.
For now I am going to assume it cant be saved and will look for a spare powerhead. This will be a fall or winter project so I just want to be prepared.
I know I can use the 35 from 57-58 and its successor the 33.
Are there any other blocks that would drop in? What about a 40hp lark 7 from the 60s?

 

[jimmbo]

Not all of the 1958 35 HP Blocks are Compatible, as there were 2 designs of the 35 that year.

None of the 40 HPs from the 60s will fit.

 

[Jdunham]

Mine is a 25532. That model shows up with 3 others in parts manuals: 25930, 25931, and 25533. I think the 259## are big twins. Which of those 3 are ok?

Without knowing all the compatible model numbers, are there visible identifiers that I can use to find compatible blocks?

 

[Jdunham]

Well, I got too curious to wait so I took it apart.

I have not yet split the crank case. I want to do some more browsing in my service manual to make sure I don't break anything when I do it.
I learned a bit more while tearing it apart:
First, as expected after 63 years, the coils are shot. Cracked, flaking and all around done in. I will add them to the list but wont worry about it for now.
The carb looks new inside, like it just came out of a box. It is not new, I just cant believe how clean it is. The throttle plate is bright yellow and the bore is shiny aluminum. A glance into the reed plates is similarly pristine but I did not take it apart.
I also noted that the crank is NOT seized. There is just enough play in the rod bearings that I could tell it was moving when I still had the flywheel on. (Hope the play isn't a problem) There is corrosion in there but I have my fingers crossed that it hasn't got to the bearings or journals yet.
I dropped the lower unit and found about 2 cups of acorns and a LOT of oily sand, surprisingly no corrosion. I think I can thank the 24: mix for that. I also found sand in the cooling passage on the starboard side (exhaust side I think). I am not sure how much debris should be in the cooling system (ideally none, but the the intake is just a screen) but it occurred to me that if someone ran it into a mud/sand bank and clogged it up I may have an overheated and seized block after-all.
I opened the impeller housing to check it and while distorted from sitting, it is still flexible and looks ok. I will make sure to look for a blockage and replace the impeller before reassembly if I can save the rest of the block.
The pistons are both still locked. midway between TDC and BDC. I had filled them to the brim through the plug holes with penetrating oil on 5/13/2020. So far there is no evidence that any of this is leaking by the rings. At least not enough to start to drip out anywhere that I can see.
Because of where the pistons are, blocking the ports, whatever critters deposited the acorns could not get past the exhaust side covers into the crank case.

When I found the engine, it had been stored on its starboard side. I am not sure if it was weight or a toss/drop, but the shift shaft is bent. It explains the difficulty I had in removing the cowl as the shift lever is too close. I cant tell if it is a shaft with small casting pressed onto it or if it is one piece. In either case I think I can straiten it and if not they do seem to be available.
The exhaust tube casting that the shaft runs in looks fine. I cleaned and inspected it carefully looking for cracks from whatever bent the shaft.

So, next step is to split the crank case and take the rods off the crank. Is there anything to watch out for here?
What about getting the pistons out? I think, given that both are stuck midway, that the least damage would be done by pushing them down and out the bottom. I don't want to push any corrosion up and score the cylinder walls above the ports. Is there any reason NOT to go that direction?
I have access to a 20 ton press but am hesitant to just start pushing on them. I may have our local engine shop do that and then have them assess the bores/pistons for reuse.

 

[racerone]

Pistons do not go out the bottom !

 

[Jdunham]

Bummer, so I have to push them through the undamaged part of the bore.
What is going to be the least destructive way to accomplish this?
I will continue to let them soak for a while.
Is there anything that will eat at iron oxide or aluminum oxide without eating at the good steel or aluminum?
I have used household vinegar and metal rescue on other non critical parts of other machines but both do affect the good metal a little bit if left long enough.
What should I use to attack the carbon deposits?
If warmed slowly, what is going to expand more? the pistons or cylinder?
I could submerge the cylinders and pistons in a pot and get them up to 180F or so.
To avoid the risk of leaving water in bearings, I could use cheap cooking oil, I would only need 2 gallons at most I think.

 

[racerone]

????-----Put the block in the coldest / deep freezer you can find.-----The piston shrinks more than the cast iron sleeve !------Do you have the cylinder head off at this time ?----Do you have the block off the exhaust housing at this time ?

 

[Jdunham]

The powerhead is off the exhaust housing and on my bench.
The head is still on to contain the penetrating oil until its time to try to get the pistons out.

 

[Jdunham]

I located a couple of donor motors. I originally planned on just getting the other 57 lark for parts, but it was too complete for that. I also picked up a 56 johnson 30.
I put the powerhead from the 30 into my original 57 lark. Running great but I haven't done high speed tuning yet.
The remainder of the parts from the 56 30 will let me complete the other lark.
The real issue with the second lark is the color. Metal flake pink...at least I can play around with some colors.

I will keep looking for a 33 from 65-71 so that I can get a little more power and run it at 50:1. But at least I can get on the water while I search.

I will probably still tinker with the original block. Who, knows, the pistons may eventually come out with no damage to the cylinders.