6hp Johnson 2 stroke overheat need to change pistons?

Geauxfish11

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I have a 6hp Johnson 2 stroke that overheated. I was told by the repair shop that it would cost $1000 to replace pistons, gasket, and bore cylinders. Since that is more than the motor is worth I declined but I am going to try to fix it myself. My main concern is if I need to bore the cylinders and if I need to replace pistons. Compression in each is around 70 right now. I will attach pictures this afternoon of the pistons and cylinders so that y'all can hopefully tell me what I need to do.
 

raczekp1

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

look for used powerhead, its cheaper
 

boobie

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

Does it still run ?? Or did it run after the overheat ??
 
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nwcove

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

I have a 6hp Johnson 2 stroke that overheated. I was told by the repair shop that it would cost $1000 to replace pistons, gasket, and bore cylinders. Since that is more than the motor is worth I declined but I am going to try to fix it myself. My main concern is if I need to bore the cylinders and if I need to replace pistons. Compression in each is around 70 right now. I will attach pictures this afternoon of the pistons and cylinders so that y'all can hopefully tell me what I need to do.

does this repair shop happen to sell new motors?????
 

Chinewalker

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

Tear it apart and inspect the pistons and bores. At this point, it won't hurt anything to look. 70 psi shows it may not be completely shot inside and a solid freshening up with pistons & rings may be all it needs. If the bores are within round tolerances and aren't boogered up, they may only need a light honing. Might be able to find some used pistons on eBay. Install some new rings, and a new waterpump kit, and you MAY be on your way.

Finding a used powerhead might be the way to go, too, depending on your level of commitment and budget...
 

F_R

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

In all fairness, depending on how hot it got, the shop may be right. Can we assume they did a decent inspection? At any rate, a motor that has run hot should have all the head and exhaust gaskets replaced. Maybe it scored the pistons, maybe it didn't. Depends on how lucky you got.
 

Geauxfish11

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Pictures before clean up

Pictures before clean up

http://s751.photobucket.com/user/Ge...[user]=139777279&filters[recent]=1&sort=1&o=0

I have attempted to attach the link above to the photos of the cylinders and pistons. The pictures are before cleaning I didn't take any afterwards I will try to take some tomorrow.

Yes, the motor still runs just take a lot of pulls to get it started, has strong fire.

While inspecting the motor I thought that the cylinders and pistons looked good after cleaning. I didn't see any damage but I am no expert. I did notice that the head gasket had been damaged and that the gasket for the thermostat cover had rotted. I trust the repair shop I just think that they take everything that could possibly have been effected and attempt to fix it which makes it cost a lot more. I just want to make it run strong again.
 
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boobie

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Re: Pictures before clean up

Re: Pictures before clean up

Put a new head gasket in it and try it. Make sure all the surfaces are clean and flat.
 

dkonrai

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Re: Pictures before clean up

Re: Pictures before clean up

Put a new head gasket in it and try it. Make sure all the surfaces are clean and flat.

+1 walls look good i dont see any scoring on the walls. i say slap on that head gasket and cross your fingers.

blown gaskets are pretty common, and you may find that the motor will have better compression numbers after the new gasket. good luck!

dino
 

F_R

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

Your choice. Slap on a new gasket and try it or include the exhaust cover gasket while you are at it. The danger in ignoring the exh gasket is it may squirt water into the exhaust ports and slowly destroy the powerhead. Besides, once the exh cover is off you can see if it scored the piston skirts and rings. You cannot tell that by simply pulling the head. The exhaust side of the pistons is the hot side and where damage happens first.

It would appear the shop did not do this, right?
 

Geauxfish11

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

http://s751.photobucket.com/user/Ge...[user]=139777279&filters[recent]=1&sort=1&o=0
I took your advise and ordered the gaskets for the thermostat cover, head, and for the exhaust cover. I also found that the thermostat was stuck open so I ordered another thermostat.

Please look at the new pictures of the piston rings taken from the inside of the exhaust. I did see some scratches but couldn't see any damage to the rings. Also when the flywheel is turned the pistons make a suction sound so I think the seal is good, but I definitely want your opinions.
 

raczekp1

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

you also need to flaten the head surface, just put sandpaper on piece of glas and slowly do round movement
 

dkonrai

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

wow that lower piston looks rather bad.. without actually being there, it seems that there is some major scoring on that piston. some minor wear on the top, but that lower...
 

Geauxfish11

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

I've already sanded down the head cover. Just waiting on the parts now.

With the pistons as they are in those pictures do you think I need to replace the pistons and rings, or just the rings or do I need to replace anything besides the gasket?

Also what would be considered good compression for this motor? It's a 1987 model J6RCUD.

Also wanted to know should I use a sealant on the gaskets or just put the gasket on by itself?

Thanks
 
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raczekp1

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

i had low hours motor from 1987, compresion was 140psi(9.5 bar) in both holes
 

Geauxfish11

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Re: 6hp Johnson 2 stroke overheat need to change pistons?

Got her running again compression is 100 psi in both cylinders.

Thanks for all your help
 
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