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I BLEW IT!! 1980 20hp Johnson BURNED DOWN!!

J

Jhanratt

Regular Contributor
So I really blew it! I have had this 1980 Johnson 20 for about 20 years. It was a crusty old salt when I bought it but it ran like a champ and served me well. I changed the gear case oil annually and it was always milky.

This year I decided to spring for a set of seals and tore down the lower leg unit. I stayed up until 1:00 am getting it back together. I took it for a test run today but failed to notice the tattle tale was dry.

I ran her wide open until she stumbled. Then as soon as I noticed a problem I hit the kill switch. Opened the cover and let the smoke out.
Rowed home and found the copper water pipe was not lined up in motor housing. NO COOLING WATER.

Now it won't start compression at 50psi.

Time to part out??? or is there hope. What is it likely to need?

Yes I know better!!! Stupid overtired mistake.


Thanks


Jeff
 
Last edited:
kimcrwbr1 said:
http://www.ebay.com/itm/NIB-Johnson...803-/301355912321?hash=item462a364c81&vxp=mtr
Click to expand...

I have attached a couple of photos. The upper cylinder is scored but I think it will be ok. I am not really experienced with working inside of engines. I am more of a pull and replace components kind of guy.

Please tell me if I am wrong.

Head is warped. I sanded with 220 on a sheet of glass. outside corners clean inside not touching paper yet.
Keep at it?

I will confirm model but I recall J20CRCSA.
 

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by the way I can feel the score at tdc but down a 1/4" I cant feel it but you can clearly see it.
Head bolts were surprisingly loose.
Watery oil in both cylinders.
 
upper cylinder has the score but the rest is good.
lower cylinder is all good.
Got hot enough to melt wire sleeve on cdi. Wires OK inside tho.
Good strong spark still.
 
I sanded for hours and it is flat now. Had to go down to 80 grit and work back up to 220.
I ordered the gasket and confirmed my part number changes up and crosses over to 18-3803.
Compression was dead even but I think the cylinders were leaking across.
The last place to sand out was between the cylinders.
I'll file and scotch brite tomorrow.
Working late got me in this mess!

THANK YOU for your EXCELLENT assistance.

Jeff
 
The piston is damaged and that motor needs to come apart.--------There are no " band aid solutions " for that kind of damage !!
 
Ok all sealing surfaces nice and clean.
Threads on bolts and block chased with tap and die (more accurate torque).
cleaned up the groove at tdc with a little 2000 grit.
Ready to re-assemble. Just waiting on the gasket.
Fingers crossed I can get a few more years out of it.
I will post back either way.
 
Racerone

I can only hope it holds together a few more years. It is too rusty to spend any money on. likely very high hours too. Photo looks worse than it feels.

Thanks
 
pictures of the cleaned up head, cylinder, and block.
think it will be ok?
 

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I think I'll just put it together and run it as long as it will go. The prop shaft and main shaft both have pitting on the seal areas. I doubt my new seal set will hold together for long. I just don't think this is a good candidate to spend time and money on. Seems sad after 20 years but done is done. As far as stranding me. I mostly use it for fishing on small heavily populated lakes and a bit of knee boarding.

I used to run 1 hour out on deserted ocean with it but I bought a trophy for that quite a while ago.

Thanks for your help and advice.
I let you know how it runs when I get it together.

Jeff
 
I just re-read. Your post. Cylinder walls are smooth. No Catch on fingernail at all. but I agree there is metal between the rings and probably a burr or two at bdc.
 
So I am waiting for a head gasket and I got to looking at the motor and part diagram. Could I not remove the carb side of the crankcase half and remove my existing pistons and clean them up carefully and re-install. My labour is free and it doesn't even look like there is a gasket between the case halves.

If I mark the con rods location and ring location, I should be able to cleanup delaze and re-install right?
I have ring compressor and ball hone in my shop already.
Case halves must use form a gasket?

Thanks

Jeff
 
IT LIVES!!!!!
Thank you.
It is idling in a bucket of water right now.
It has a small water leak from the water jacket on the side. That might not be new?
I will pull that bolt only and seal it. I will test at the lake when I can and report back.


Jeff
 
Okay just got back from the lake. I had to try it.
It ran like a champ. 1/2 hour at idle in a bucket at home at a little better than an idle.
1 hour on the lake mostly w.o.t. good top speed. good idle. good mid range.
aviation form a gasket sealed the one leaky water jacket bolt.

So if the scoring gets worse and kills it will it likely be a slow death with reduced power and weak idle or will it die quickly?
I have a cub scout meeting planned for next week (knee boarding) and it would be bad if it failed then.

Thanks
 
Thank you for the solid advice. Here is a long term update. It's still running like a champ pulling kids on tubes at W.O.T. and idles down slow enough to troll. No sign of any damage despite the over heat. I'm amazed but its holding up like there was no damage.
Again Thanks to everyone. I really appreciate the advice!

Jeff
 
The scoring will not get worse unless a different issue occurs such as no oil, too lean or another cooling issue. Great job resurrecting the dead!
 
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