Hello, I have used this forum to help repair 2 outboards. I amnow in the process of rebuilding my 1980 75hp johnson model #J75TRLCSA. The reason for the rebuild? I did all of the checks necessary and found upper cylinder was down on compression. Top70 middle 110 bottom 110. I removed the head and found the piston was melted on the exhaust side to the piont I could see the ring. I have since completely disassembled powerhead and removed lower unit(water pump impeller was toast). After checking all parts closely here is what I found:
1. carbon buildup on piston and head where piston is melted
2. rings on melted piston were in tact but stuck in melted area and loose around the rest of piston
3. some minor? pitting on crank rod journal of effected piston
4. more carbon buildup in exhaust housing
My questions are:
Do I need a new crakshaft?
What doI use to remove carbon buildup in exhaust housing?
Thanks for any help you can offer,
Chris
1. carbon buildup on piston and head where piston is melted
2. rings on melted piston were in tact but stuck in melted area and loose around the rest of piston
3. some minor? pitting on crank rod journal of effected piston
4. more carbon buildup in exhaust housing
My questions are:
Do I need a new crakshaft?
What doI use to remove carbon buildup in exhaust housing?
Thanks for any help you can offer,
Chris
