decarbing a motor question

[MASTER Brian]

I have a 1977 Evinrude 70hp engine. It's sat for about 5yrs, so I have ran about 1/2-3/4 gallon of decarb mix through her. With the lower unit tilted down, black sludge keeps running out and it was still smoking mid way through the 3rd time. We had to stop due to getting dark and fuel running low.

I looked at the plugs and they look good, but pistons still have carbon on top. I'm guessing I should run another 3/4 gallon of mixture through it or until the smoking stops. I'm also guessing the black sludgy stuff is just the carbon burning off.

Am I correct???

Thanks for any help.

 

[Al-53]

Re: decarbing a motor question

yes the black gunk is carbon....once you get her on the water the piston crowns clean up....

I like doing the de carb when running on the water..I go about 3000 rpms tops...smokes like crazy...but cleans good ....I think people think I am there to fog for mosquitoes...lol...you can go early morning when every one is asleep...

I use a 3 gallon portable tank with 1 gallon mix..run that out and switch to built in tank...when i get home i pull the plugs..nice and shiny inside...clean ..clean....

AL