Thanks! Just a quick follow up note: 3 years later this outboard is still running great. I'll try acetone for cleaning next time i do something like this, but the sanding does not seem to have had a negative effect...

Awesome man! Hoping to do the same to my 40hp. Oh, and that aint no torque wrench dude. LOL

Thank you for posting the video :)!

Thanks for the video! What led you to diagnose the head gasket? I have a Yamaha 15, I’m getting a weak stream at the tell tale, and very hot exhaust. I think a previous owner exploded the impeller and a cooling jacket may be clogged. I will try your trick with the spark plug removed

Do you put a thin layer of gasket seal on both sides or just the head side?

Cool video :) there is supposed to be an anode where your calcium build up is though 😅

The smoke was probably from your wd40, good job.

I have a question im stuck beacuse my botom barral is pussing out heaps of water will that case water tnough out that plz help

i would never sand it, although this was super corroded. I would use an etch like acetone or something instead.

this video has great detail: kzfaq.info/get/bejne/hLx8e62E2ryscWg.html