I heard about a modification that gives the 500 EFI 65 hp after this conversion. Are making the throttle body larger?

Clark

http://www.azspeed-marine.com/marine-11.html

and it's 25HP, haven't heard of any at 65

What VB said. You need to reprogram the ECU with them too, about $800 total to AS&M, plus local money to have intake machined.

My guess is that 20 of those hp come from the computer reprogram.

THAT WOULD BE BOOSTPOWER USA PHONE#805-376-6077 THEY HAVE A COMPLETE HANDS ON HOW TO IN FAMILY AND PERFORMANCE BOATING JULY 2002 ISSUE THE KIT INCLUDES A LARGE MOUTH MONO BLADE THROTTLE BODY, MSD IGNITION PHENOLIC SPACERS WITH BOLTS AND REPROGRAMING OF YOUR OEM ECU LOOKS GOOD TO ME PUT IN PHONE CALL TO THEM BUT THEY DID NOT GET BACK TO ME WITH DETAILS LIKE PRICE BUT DOSEN'T LOOK VERY EXPENSIVE FOR 65 HP.

i saw the article seems a little much 65 hp, arizona speed has prob same kit?