NMAC.

Narrative

DURING CLBOUT FROM SEA AT ABOUT 7000' ON AN IFR FLT PLAN; THE ATC CTLR RPTED TFC AT 1 O'CLOCK AT 8700' OF ALT. THE CTLR TOLD US TO MAINTAIN 8200' TILL CLEAR OF TFC; WHICH HE WAS NOT CTLING. WE CALLED THE TFC IN SIGHT AND SAID WE WOULD MAINTAIN VISUAL FROM THE ACFT. THE CTLR CLRED US TO CLB TO AN ALT OF 23000'. WHILE CLBING; THE VFR ACFT AT 8700' APPEARED TO CHANGE COURSE TOWARDS US AND CLB A BIT; TO ABOUT 9000'. THIS CAUSED OUR ACFT TO ALTER COURSE SLIGHTLY; AND CLB AT A FASTER PACE. THE 2 ACFT CAME WITHIN ABOUT 300' OF EACH OTHER. OUR ACFT HAD LNDG LIGHTS; STROBE; NAV AND WING ANTI-ICE LIGHTS ON FOR COLLISION AVOIDANCE. THE VFR ACFT NEVER SAW US. I FEEL THAT NO ONE WAS AT FAULT IN THIS SITUATION. IT COULD NOT HAVE BEEN AVOIDED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES SECOND ACFT WAS AN SMA; NO LIGHTS ON. EVEN WITH CLOSE PROX RPTR FEELS NOT A REAL PROB AS THEY HAD TFC IN SIGHT CONSTANTLY. HE DOES NOT CONSIDER ALTERATION OF COURSE AND CLB RATE AS EVASIVE ACTION.