Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

rothfm

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My 115 teardown (first time) went smooth and uneventful. I had 1 outter ring break (prior to my purchase) it tested fine and had good compression. When I got into it, it Had no damage other than a pocked head and Piston. Walls very smooth.

My plan was to replace offending Piston & Head, hone and ring all 4 holes. However, Since I cant be sure of any previous work, I cant be sure what sizes are in there from the past.

I'm assuming a good practice would be to baseline the whole thing--Meaning I should take it to be measured fully (pistons and holes). Rings are sized to specific Piston sizes right? If there was an oversize in there already I wouldnt know it, and I'd probably put the same rings on all 4 inadvertently. Going to have them clean it, and take out 2 broken Mount bolts too.

Ha...as I write this, I'm answering my own question I think!!!!!

Also, while this is opened up-is there anything else I should replace that one would consider critical. I'll spend some, but dont want to replace everything just to do it.

Thanks
 

Capt Ken

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Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

Clean the top of the pistons. If it has been bored before, the pistons usually have the size stamped on them. .20. .30. Or .40.
 

bob johnson

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Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

you would certainly need to tell ius what year and model # the motor is...then we might be able to tell you right off what the dia is supposed to be from the factory.

bob
 

rothfm

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Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

you would certainly need to tell ius what year and model # the motor is...then we might be able to tell you right off what the dia is supposed to be from the factory.

bob


Thanks, 1984
 

rothfm

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Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

Clean the top of the pistons. If it has been bored before, the pistons usually have the size stamped on them. .20. .30. Or .40.

Hmm, Thanks. Will clean the tops and see. I'm thinking it will still be good idea to take it to be fully measured and go from there. Thay way I'll truely know the shape of the holes and know what parts to purchase.

thanks for the feedgack
 

Faztbullet

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15,589
Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

I'm thinking it will still be good idea to take it to be fully measured and go from there.
That the only and correct way to rebuild one....
 

bob johnson

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Joined
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4,304
Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

My 115 teardown (first time) went smooth and uneventful. I had 1 outter ring break (prior to my purchase) it tested fine and had good compression. When I got into it, it Had no damage other than a pocked head and Piston. Walls very smooth.

My plan was to replace offending Piston & Head, hone and ring all 4 holes. However, Since I cant be sure of any previous work, I cant be sure what sizes are in there from the past.

I'm assuming a good practice would be to baseline the whole thing--Meaning I should take it to be measured fully (pistons and holes). Rings are sized to specific Piston sizes right? If there was an oversize in there already I wouldnt know it, and I'd probably put the same rings on all 4 inadvertently. Going to have them clean it, and take out 2 broken Mount bolts too.

Ha...as I write this, I'm answering my own question I think!!!!!

Also, while this is opened up-is there anything else I should replace that one would consider critical. I'll spend some, but dont want to replace everything just to do it.

Thanks

from all that i have heard, one thing to make sure that is new and working properly is the water diverters...

I dont have them on my motor style...but those crossflows had them and they seemed to be a problem area

bob
 

rothfm

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Joined
Sep 26, 2006
Messages
913
Re: Rebuild Question Johnson 115, piston sizes. hopefully not a dumb question here

from all that i have heard, one thing to make sure that is new and working properly is the water diverters...

I dont have them on my motor style...but those crossflows had them and they seemed to be a problem area

bob

Oh yea, very familiar with the diverters. I was actually surprised to see they are still round. Replacing anyway. A very important item for sure.

Thank you. Got all the pistons out, everything labeled and in bags. Going to take it to a shop for cleaning, and measuring.
 
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