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Lower cylinder failure

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Fordrulz

New member
Hi guys. I have a 1997 Mercury mariner 15hp. Last spring the cylinder lost compression. How hard is the rebuild? Any tips or a manual to follow? Wondering what might have caused the failure so it won't happen again? Thanks for any help
 
Do you replace impeller every 3 years or so ?----Mixing gas and oil at 50:1 in your tank ?-----Step #1 is to take it apart for evaluation.
 
Gas is always.mixed 50:1. Honestly I have never replaced the impeller only due to the fact that there is always a good stream of water spraying out. I will disassemble and inspect soon. Anything special about the teardown? I have not rebuilt a outboard..
 
Water pump replacement is not too difficult. A service manual would be a big help for your first time, not to mention any other issues that might arise down the road. YouTube has lots of videos that will give you an idea of what your getting into. As far as determining why you lost compression and tearing into that issue will require more skill and knowledge, again a genuine Mercury service manual will give you some insight of what’s involved.
 
1994 and up 15hp are Mercosil blocks. If cylinder has ANY scuffing or damage it will have to be sent to a cycle or marine boring repair shop. You CANNOT use a regular hone to clean cylinders or a standard cutter when bored.
 
So I finally got around to tearing into this engine the cylinder and the rings and sidewall of piston look good. I found a hole in the top center of the lower piston not sure where to go from here or what would have caused this any ideas? Thanks!
 
Fordrulz said:
So I finally got around to tearing into this engine the cylinder and the rings and sidewall of piston look good. I found a hole in the top center of the lower piston not sure where to go from here or what would have caused this any ideas? Thanks!
Click to expand...

Just out of curiosity, how does the bottom cylinder piston look?
 
This one is the lower cylinder. The top one looks good but I noticed a small pin hole in the center of that piston looks to be a factoy hole it is uniform not sure though?
 
most outboard dealers recommend replacing the water pump impeller every other year. they are not expensive and if you have a little mechanical ability you can do it yourself. over the years that rubber impeller weakens and you lose water pressure. The lack of cooling water could contribute to the cylinder failure. there is a company in Alabama called OBR. they sell powerhead replacements for about the same cost of having one rebuilt.
 
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