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Interesting hole in crankcase...

Jay1234

Regular Contributor
Hey all,

Was out with my son doing our usual perch fishing tonight. Boat running fantastic like always. She is powered by a 1968 55 horse, which I absolutely love. On the way back in the exhaust note changed, followed by the boat slowing to a crawl. Shut it off and ran back to the launch on the trolling motor, and upon pulling the engine cover found a 1" square hole in the crankcase... I totally understand the age of the engine, but I am insane with maintenance on it. What would cause this?

On another note, racerone, the company I work for is headquartered in Toronto, and if you have a power head that would work on her, I am willing to pay.
 

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Simple------Many of these motors suffered the same fate.-------The early motors tended to break a piece of the piston skirt.-----This piece would get jammed between the connecting rod and the case.------The case goes BOOM.-----The fix is a block with thick wall pistons.-----I have 60 HP block with 3 new pistons, and I have to ponder on the logistics here.
 
Appreciate it. Let me know. Love to keep her running for some more years. It's been a beast of motor. We've put a ton of hours on it over the years.
 
Yes seen this before, I have repaired these blocks, but no pictures to show...Do you know a good welder?
 
Morning Timguy,
I was gonna go that route and rebuild it, but I got lucky and found a good long block for a good price. I surprisingly had quite a few offers from local outboard shops that had some they were still hanging onto. Going to swap all my stuff over on to that block and hopefully get back on the water a time or 2 before there's any ice. I also figure that way too I'll have some spare parts around, as only the #1 piston and the crankcase was damaged. I'll weld up the holes just in case I need it.
I did notice after I took it apart that the other side of the case also had sustained damaged. There was a hairline crack just opposite the rather large hole.
 
There is lots of blocks around here too. I wonder if replacement pistons will outlast these OEM's. Wouldn't want this to reoccur. Lake Superior is still open, as soon as ice forms, the next day the wind destroys it. Probably no ice fishing till Feb. Boats are all buried with over 2 feet of snow. Next year hope to make room inside for my little Alumacraft 20" transom. Fun to be the only one out there fishing in the winter. Sure to have 2 motors and don't fall overboard, eh? Probably be your last trip.
 
No doubt. Water was 36 last time we were out. It's so calm up here in the winter, we love getting out fishing. Just us, the duck hunters and few other crazy fishermen. Never leave home without the Minn kota batteries charged. I was curious about the replacement pistons myself. I'll have to look in to that some.
I do believe the block I'm getting is a 60hp model, from what I gathered from racerone the 60hp pistons are better? Or is it the aftermarket ones?
 
Nope---The 60 HP blocks have 3 intake ports as opposed to 2 for the 55 HP of 68 / 69.-------There were lots of failures on the factory 60 HP pistons too.-----They sorted this problem out in the mid 1970's on the 70 HP models.
 
Gotcha. Are the Wiseco pistons any good? And what would the difference between the Wiseco 3015PS and 3115PS? They both show as a good part number for my engine.
 
This site needs to do a little work on it's parts referencing then.. it's all good though my local outboard shop, the owner of which thinks I'm nuts for everything I put into this engine, is bored this time of year and said bring the parts in. He'll look everything over and hook me up with what I need. He's fixing the crankcase as well.
The long block I was going to get I put in hold for the moment.
Thanks a bunch faztbullet.. I was actually just about to order 3 of them. The price from the shop for the omc pistons was double the wiseco. I didn't mention to him I'd been looking elsewhere... I'll be buying the old stock he has though.
 
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Your friendly parts man will likely know that there is an issue with the diameter of the wristpin.----And he may know what to do about it too.----Do you have a tachometer in your boat ?----What boat and what pitch prop are you running ?
 
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He's got pistons for a 68 55hp.. I don't understand why half your posts are riddles... I totally understand I'm an idiot for trying to keep this engine going. But I have reasons.
It's on a 68 aerocraft. The prop is a 13 3/4 by by 13 I believe, could be off on that I haven't looked in a while. Boat runs 30-35 mph on a good day. Never had a tach on it.
 
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I try to make folks think.----Steer them in the right direction.---Prevent them from making expensive mistakes.----Often my advice falls on closed minds.
 
I understand and appreciate that. I have spent my career doing on site service work for broken down equipment. I don't make an effort to make anyone feel stupid.
You also said you had a block with new pistons available.
I am far from a closed minded person.
 
Thats why I asked where you found pistons...the one's listed on this site are NOS pistons(new old stock) and no reference to Wisecos. Cannot even find them listed in Wiseco for your year engine.
 
If I look at the crankshaft group parts list for the 1968 Johnson 55 TRL-10R, it shows #10, piston, original part #0382274, superceded by part #0386251, which when you click on the 386251 piston, on the bottom of that part description is says equivalent to Wiesco 3115PS, 3015PS. When I did a further search off this site on those particular Wiesco pistons they show for a Johnson 3 cylinder, 3" bore. I'm just a little confused is all.
 
s-l400.jpg

These are the pistons I found. I apologize if I offended anyone last night, but I try to do as much research on something as I can before I post a question. Just looking for a little guidance from the pros that do/did this daily.

Thanks
 
Did a complete teardown tonight. #1 piston was obliterated.. #3 had cracks down both skirts. Cylinder bores look good.
My pistons have 3 rings. The replacements I'm seeing, including the used ones the shop showed me, have 2. Can you guys educate me on the difference?
 
1) Have the bores "miked" as at that age they are highly likely past the wear limit. of .003
2) Check the wrist pin size and height on the 2 ringers as may not fit.
I had a customer in the late 80's that I rebuilt his engine with DMI pistons that was "listed" as direct replacements. I found the wrist pin location was offset by .120 that prevented the piston from reaching top of bore. Had to find a used block and use NOS pistons to repair. My advice is to check and measure EVERYTHING!!!
 
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Thanks much for the reply. I just dropped everything off at the shop tonight after work and spent an hour there just talking..
He's going to check bores for excess wear, and give everything else a look over. I told him let me know what I owe you for the l your time, he said he's just glad to see that some people are still willing to work to keep things going in this throw away society.
Talking face to face with someone who worked on these when they were new, definitely see s little excitement every time I go there. I certainly pay, but I have bought nearly everything I've replaced on it from him over the years.
So anyway, almost done with the sentimental crap.. but, I know the core group of guys that keep this forum going were or are self employed techs, and the time, research, and effort that you put in to helping us guys, for free, that want to simply fix things, is incredibly valuable to all of us, regardless of how we may come across at times.
 
Yes for most of these guys here are retired and have the extra time to try and help. I am pretty experienced but still use this info for my own gain too. Right, self employed since 1974, always gaining knowledge here. Sadly perhaps everyones favorite tech, and one of my mentors, recently stepped down, but the records still show his answers over the 10 years on Marine Engine.
 
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Makes sense for sure, always room for a LITTLE improvement, eh? I shoot for 60 years....if possible. My 1965 Evinrude Fisherman is still running strong. Probably only sat out a half dozen seasons in all the years....bought it new....Dad bought it as my "guide" motor.
 
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