1999 Mercury 25HP low compression bottom cylinder

pitts1371

Recruit
Joined
Jun 19, 2016
Messages
1
I have recently purchased a 1999 Mercury 25hp tiller handle with electric start from a yard sale. I bought it for $100. The guy told me the bottom cylinder was burned up. I've been looking into it and I've seen mixed information. I've seen some say it can be bored .040 over and some say it can not be bored. Some are saying it is a blind bore and can not be done. If anyone has any input on this please let me know. For $100 I figured it was worth a shot to try and fix it. I am not opposed to fixing the motor because it is in great shape.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
A quality machine shop can bore the motor out. It is a blind bore and Mercosil Coated so make sure you find a GOOD machine shop. .040 is not going to happen take it apart and find a machine shop see what they say and go from there.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Mercosil is not a coating it the material the block is made from. You will need to take to a good cycle repair shop as it take a special cutter bit and diamond hone to bore it. A lot of the foreign cycles use this type of cylinder. Also these are really bad about going out of round if hot so have them mike the other cylinder, anything over .003 out of round needs bored....
 
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