Re: spark plugs 6 hp evinrude 1990
Champion QL77JC4 are the recommended plugs
The NGK equivalent is BZ7HS-10
The Q in the Champion number and the Z in the NGK number denote inductively suppressed plugs. They are what you should be using.
B7HS-10, which I guess is what you meant, is not inductivly suppressed but they are what I have in my 6hp. I notice no difference between those and the original Champion plugs.