130hp Yamaha 2-stroke rusty cylinder

dfrants

Petty Officer 1st Class
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Jul 26, 2008
Messages
393
I picked up a 1993 130hp Yamaha 2-stroke. The compression numbers are pretty good, 125-130lbs in each hole. Starts and idles nice but will kill sometimes just before planning off. Got a leak down done and the #4 cylinder was at 21%. So I pulled the head and the #4 hole has a rust spot on the top of the cylinder wall. Is it possible to remove the rust and smooth the wall without doing a complete tear down and rebuild?
 

Fishandboat

Cadet
Joined
Aug 11, 2019
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12
You can clean the rust and polish a little. Just try not to remove alot of metal. Maybe 600 grit wet dry. Or you could even pack a rag or paper towels intop the piston push it down and gone the cylinder. The thing is that the rust will wear on the rings. I would just clean it up some and dont worry about it. It should not make it run bad. Also if the cylinder has rust posible one of the rings may be stuck from rust.
 

dfrants

Petty Officer 1st Class
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Jul 26, 2008
Messages
393
Thanks for the tip! I used a green scotch brite pad and WD-40...the rust is gone. Going to try to polish the area alittle with ultra fine wet dry sand paper, order a new head gasket and give er a try.
 

QBhoy

Fleet Admiral
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Mar 10, 2016
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8,343
Was the rust from water at head or the oil tank ?
quite common for the oil tank to take water in if left with a bilge full of water.
 

jimmbo

Supreme Mariner
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May 24, 2004
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13,467
Don’t do any polishing. The rings will do it. If it was just a light bit of surface rust, I wouldn’t have even been concerned. The WD40 and Scotchbite treatment was fine. If you are still worried, just rub a bit of TCW-3 on the area
 

dfrants

Petty Officer 1st Class
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Jul 26, 2008
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393
I'm not sure if the head gasket was or not now...I assumed it was but I just removed the little tube under the oil tank that is mounted on the powerhead and found alittle water in it...
 

dfrants

Petty Officer 1st Class
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Jul 26, 2008
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393
Im going to be putting the head back on this weekend...whats the correct torque setting for the head bolts?
 

QBhoy

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Mar 10, 2016
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8,343
I'm not sure if the head gasket was or not now...I assumed it was but I just removed the little tube under the oil tank that is mounted on the powerhead and found alittle water in it...

Thought it might be the case. These engines are as reliable as they get. Only something like water getting into the oil feed tank (that sits in the bilge) can be the usual cause of failure like this. Happened to a boat I bought cheap for this very reason. Same engine.
 
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