Powerhead Rebuild

[RodneyReed]

I'm in the middle of rebuilding the powerhead on an old 1977 Johnson 55 outboard. Upon disassembly, I noticed that some of the cooling passages had paint or some other coating on them. Some of the coating had flaked off, and there was a fair amount of dirt, debris and corrosion in the cooling passages as well (after 33 years that's probably to be expected).

I've sandblasted all of the cooling passages, and the outside of the head and block, and everything is now (almost) perfectly clean. I'm definitely going to paint the outside, but I'm wondering if I should paint the inside of the cooling passages (or use some kind of coating) to help combat future corrosion, or if I should leave it bare as the paint may affect heat transfer.

If anyone has any experience in any of this, any advice would be highly appreciated.

 

[oldcatamount]

Re: Powerhead Rebuild

That paint inside the passage ways is probably the original factory primer paint. Personally, I wouldn't paint the passageways again as the paint may flake off and clog up somewhere. Since you have sandblasted everything, it seems to me like that would be enough.

 

[RodneyReed]

Re: Powerhead Rebuild

Thanks, oldcatamount. That's kind of what I was thinking, but I wasn't sure. I've rebuilt a lot of motorcyle engines and a few car engines, but I'm new to the outboard world.