1985 Johnson outboard 25 hp problem

[Md20mad]

Hello every one!

I have this old fellow "BJ25BALCOS" and a month ago I was driving back to the harbor when I felt the engine was dying then I stopped it. Where was a lot of white smoke coming from the engine cover then I removed it to allow some chilling as it was so hot. The feul tank was almost empty so I added some feul that I got with me and tried to launch it again but I couldn't. The coast guards pulled me out to the harbor. Next day I tried to start the engine but it was so difficult and it ran but after so many robe pulls and with the acceleration on N but full power. No water was coming out. So I stopped it. Cheching the impeller, it needed to be replaced. But i intend to replace the thermostat as well. Today I removed the cylinder head gasket to check so i found it not damaged but one of the pistons was as if exploded. (Picture attached). I dunno if that's normal or not. Please advise and thank you pretty much.

 

[racerone]

Mtor needs to come apart for major work.

 

[joereeves]

Your picture of the damaged piston indicates "Pre-Ignition". The mention of white smoke indicates "Water". I suspect that perhaps the head bolts weren't torqued properly which resulted in a damaged head gasket, allowing a fine spray of water to gain access to the cylinder, in turn resulting is what we see... the damaged piston. There are other area of which water could have gained access but this is the most logical & common.