AN ACR B737-200 HAD TO TAKE EVASIVE ACTION TO AVOID A LONG EZ DURING AN ARR AT KOA. THE RPTR COMPLAINS OF A LACK OF RADAR COVERAGE BELOW 5000 FT AT KOA.

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CLR; 50+ MI DAY. CLRED VISUAL APCH TO KEAHOLE-KONA AT RWY 17. VFR TFC (A LONG EZ?) PICKS UP A SQUAWK FROM CTR FOR VFR TA'S AND STARTS A CLBOUT FROM ARPT TO NW. THERE IS NO APCH/DEP RADAR AT KONA AND CTR PICKS UP DEP TFC BTWN 4000-6000 FT. CAPT AND I STARTED LOOKING AT TCASII TO ATTEMPT TO IDENT VFR TFC AS SOON AS WE HEARD HIS RADIO CALL. THERE WERE SAME TFC RETURNS ON THE TCASII DISPLAY GREATER THAN 15 NM AWAY TO THE E. CTR COMMENTED TO THE VFR TFC THAT HE'D 'ADVISE THE B737 TFC OF YOUR (VFR TFC) POS.' WE WERE LOOKING AT THE TCASII FULL TIME NOW AND LEVELING AT APPROX 6500 FT. CTR CALLED US AS WE RECEIVED A MOMENTARY HIT ON VFR TFC AND A 'TFC; TFC' CALL. CTR ADVISED 'TFC 12 O'CLOCK 3 MI AT 6500 FT' AND WE STARTED A CLB AS WE RECEIVED AN RA 'CLB; CLB.' VVI CLB EVENTUALLY REACHED 3500 RPM TO MAINTAIN 'GREEN' ARC. ESTIMATE 500-1000 FT VERT MISS. THIS HAPPENS A LOT AT KONA! THERE IS HIGH VOLUME CIVIL; CPR; MIL; AND PVT TFC AND NO RADAR BELOW 5000 FT. A RADAR NEEDS TO BE INSTALLED NOW TO PREVENT AN ACCIDENT THAT WILL HAPPEN EVENTUALLY!