penta 200 hp black smoke
 

hi guys I'm new here and needing some help if possible
im wanting to buy a 28 ft bertram flybridge 1982 model with twin pentas installed in 1998 and has done 650 hrs
on a quick run yesterday they started first go each but i noticed black smoke was always present out the back.
is this a major problem i should be worried about? any help would be great cheers