scuffed and scratched pistons

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adk_vfr

Seaman Apprentice
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Aug 12, 2011
Messages
47
Hey guys hows it going so i was redoing the gasket on my exhaust housing on my 1990 90hp johnson as it was leaking alittle bit when i noticed vertical scratches and scuffing on the sides of a couple of my pistons on the right side of the engine. weird thing is i havent had any problems with power or had it overheat or anything like that the plugs are also always nice and tan. Problem is you never know what somone did with it before i got it as i bought the boat used last year. So what do you guys think should i be worried i plan on just using it the rest of the season and maybe a fresh rebuild over the winter.
 
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wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: scuffed and scratched pistons

Check compression and let that be your guide.
 
A

adk_vfr

Seaman Apprentice
Joined
Aug 12, 2011
Messages
47
Re: scuffed and scratched pistons

if the compression is good would you say im good for running. on the left side the motor ive nocticed the pistons look ok even like new so thinking maybe someone rebuilt that side.
 
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wilde1j

Vice Admiral
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Apr 15, 2002
Messages
5,964
Re: scuffed and scratched pistons

What I'm saying is don't fix what isn't broke.
 
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Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: scuffed and scratched pistons

A scratched piston IS broken!
Polished and scratched piston increase the risk of a broken oil film. Cut a piston from top to bottom and study the cut in a microscope. It will look like a saw-blade! This enables it to keep the oil film intact. Scratch from top to bottom, oil gets drained away. 'Polish' it and the oil will not stick.
I would consider a change of pistons before you end up with a seized piston.
 
A

adk_vfr

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Aug 12, 2011
Messages
47
Re: scuffed and scratched pistons

Ya i hear ya there im just kinda in a place now where iver dumped money into the motor and boat already and probably will only get 4 or 5 more fishing trips at most before the boat will be up for the winter. when i will tear it down and rebuild i have a machine shop ive used on other rebuilds they bore and piston match the block and they do a good job. I just would really like to finish the season out.
 
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Haffiman

Commander
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Dec 17, 2009
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2,454
Re: scuffed and scratched pistons

Worked this long, let us hope it works out the season!!
 
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adk_vfr

Seaman Apprentice
Joined
Aug 12, 2011
Messages
47
Re: scuffed and scratched pistons

ya i hope so I gotta tell ya there is no worse feeling than seeing those scuffed pistons I thought my motor was great until i saw it and never would have know if i wouldnt have noticed the leak in the exhaust housing while running my motor on muffs after retiming.
 
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petryshyn

Commander
Joined
Oct 3, 2001
Messages
2,851
Re: scuffed and scratched pistons

"Scratched" and "scored" are subjective to the viewer. I'll bet there are more 2-stroke "scratched pistons" running out there than unscratched. Post a picture. That will take the guess work out of the equation.
 
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