Sorry to tell you, but Chuck, needs to be DINNER. His legs are yellow and that is a deal breaker for breeding. If any of the other marans you have are related to him you probably should not breed them either. Yellow legs are recessive and that means he got the genes for yellow skin from BOTH parents and even it the others don't express it they carry it.
Sorry. They are not properly breed Marans.
Rip,
The other two Marans I have are unrelated to Cluck. Can the yellow be bred out? He's the only rooster I have, lol. I'll have to run out later and take a closer look at his, and the pullets' legs.
If you want to work for about 4 generations you might could. Personnally I would get another roo. That roo will pass the genes for yellow skin to 100% of his chick. They will not express it but will pass it on to their chicks and it will be a thorn in your side forever.