JoshKeller84
Petty Officer 1st Class
- Joined
- Jul 2, 2010
- Messages
- 220
j75ecrd
j5949958
i tore down this 1984 johnson 75 that came with a boat i bought to use with another motor. I figured out the bottom carb was clogged and broke the rings off of the bottom piston, presumably at the ports, due to the lack of cylinder wall damage. it had 145 psi on top 2, 0 on bottom. i checked the bore with a scope and micrometer borrowed from my auto mechanic, and it came back pretty much perfect. Honed it out, and put in a new piston and rings on the bottom cylinder only, since I just want to get rid of it.
coated everything with oil, put her back together, and hooked it up to the jump starter on my bench. top two were 130 psi bottom was 105. Put a tea spoon of oil in the bottom cylinder and it came up to 120. did I do something wrong here, or will the compression likely come up after I break it in for a few hours? whats the likelyhood that it'll run decent now?
One thing I noticed is that there are compression numbers written on the heads, and with my weak jump starter, they are coming back the same as the written numbers, which was obviously taken before it broke the rings.
j5949958
i tore down this 1984 johnson 75 that came with a boat i bought to use with another motor. I figured out the bottom carb was clogged and broke the rings off of the bottom piston, presumably at the ports, due to the lack of cylinder wall damage. it had 145 psi on top 2, 0 on bottom. i checked the bore with a scope and micrometer borrowed from my auto mechanic, and it came back pretty much perfect. Honed it out, and put in a new piston and rings on the bottom cylinder only, since I just want to get rid of it.
coated everything with oil, put her back together, and hooked it up to the jump starter on my bench. top two were 130 psi bottom was 105. Put a tea spoon of oil in the bottom cylinder and it came up to 120. did I do something wrong here, or will the compression likely come up after I break it in for a few hours? whats the likelyhood that it'll run decent now?
One thing I noticed is that there are compression numbers written on the heads, and with my weak jump starter, they are coming back the same as the written numbers, which was obviously taken before it broke the rings.