I picked this little outboard up from a friend who gave up on it 2 years ago. Compression was about 53 lbs on both holes. It would not keep running. With a hard pull it would start firing, never speeding up, and just slow down to a stop. He put new coils, pts etc in it and replaced the head gasket, new impeller. Fuel system cleaned with kit in carb. I got the same results with it. Pulled the head and bores looked good. Head and block was true also.
I have seen that milling a head to improve comp is not a good idea, but while I was there, I made a head gasket with material 30 th thinner than the head gasket. Compression came up about 4 lbs. Just wanted to see. Then I took it all apart. Piston fit was very good with almost no wear in the cylinders. I spent a lot of time with the bore mic and feel I got good readings. I just could see nothing wrong with anything. I started to remove the rings and the first one broke. O K, I am pretty good at not breaking rings, so I took a lot of care, and all rings broke. Thought maybe for some reason they had lost some of their tension. No sign of over heating, very, very, slight discoloring of the exhaust cover. No gauling in the cylinders. So, got some new rings from Otto’s, gaskets etc and put it all together. Ran it 4 times in the tank for 15 or 20 m and it starts and runs great.
However, the exhaust cover discolored more than it was. In the first run checking it with my heat gun, it seemed to run a bit warm, 140- 175 head and block. The exhaust cover 250 +. Just to be sure, I removed the lower unit and checked the new impeller, lines etc. Back in the tank, I removed the flush out plug, lots of water, so I continued to run it off and on. Slow to fast idle mostly with a little fast here and there. While it was apart, all the water passages were already clean and I blew everthing out. Good water coming out of the holes in the down leg. The engine Temp is running lower now, 120 – 145 but not the exhaust side. I know it will be the hotter then the rest, but.
Compression is now 62 lbs and should come up a little with some use. (note I live at 4,000ft) Question, why should it discolor the exhaust cover? What am I missing. I have a much need job for this long shaft motor next year. Ideas?