502 (425hp) efi system onto a carb hp500
 

I recently purhased a complete efi system that came off of a 2000 502 with 425hp and my plan was to replace my carb system on my 1998 hp500 will this work or am i just asking for problems

Depends on your installation and rigging + who does the programming.

Why going EFI ? Remote start for cold mornings ?
LOL. Sorry...just had to. The Hp500 carb/induction package plain ol' works.

It does work but why has everything Switched to EFI? Efficiency. I have not been able to come off the $8000 to buy a blower yet so in my pursuit to buy one i might as well save a little on the way

it will work...lots of luck on tuning, as there is only a few who can seem to get it right...

Good choice. Fuel efficiency will be WAY better, especially on cruise.

My two cents- look for hp500 or hp525 EFI setup, the standard EFI will choke the hp500 carb engine...

Why would this choke the motor are the intakes different between the two i noticed that they moved the inlet for you air intake to the front on the hp500 but other then that i havent found a real difference

If you think you're gonna gain a bunch of speed, you wont.

If you think you're gonna gain a bunch of reliability, you wont.

If you think you're gonna save a bunch at the gas pump, you wont.

If you think you're gonna bolt on that EFI setup and just go boating, you wont.

In my opinion, leave the engine alone. The HP500 carb engine was a GREAT engine. If its not running properly, get someone who knows what they are doing to tune the Carb. Save your money and labor for beer and gas. Merc knew what they were doing when they made the HP500. They also knew what they were doing when they made the 502 Mag EFI 415HP. Nobody however, knows what they are doing when it comes to what you are doing.

The hp500 carb motor has a cam with 110 LSA. All of the Merc EFI motors have cams with 114 to 115.5 LSA, this might be a tuning issue.

Some of the Merc EFI cams (at least on the Mag motors) only had a 109 LSA.