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Velocity Tom

11-13-2018 06:01 PM

500 efi. Hp question

The early 500 EFI s 2000 2001 where rated at 470. Now didn’t merc get some flack for not being 500 hp . And on the later models bump it up to 500 hp with a computer upgrade ?

Wildman_grafix

11-13-2018 06:23 PM

It depends on where you measure. At the prop they say 470.

Mine on the dyno with everything on them, water pump, sea pump, wet exhaust etc, corrected were right at 507-511HP.

This was at 380 ish hours, top ends had been rebuilt around 320-330.

EDIT: Mine are 2000, electric fuel pump only model.

Velocity Tom

11-13-2018 06:26 PM

Ya I know that I vaguely remember a conversation about the later model 500 EFI is have a little hoter tune .

Powerquest230

11-13-2018 07:36 PM

If I remember correctly, output is the same for all years with some years output rated at crank and some at prop. HP 500 rated 490 at crank and 470 at prop-shaft. Something to that effect.....

QWKRN U

11-13-2018 07:39 PM

They caught flack for the 500efi only making 470 at the prop, so with the 525 they were making at least 525 at the prop.

BUP	11-13-2018 10:15 PM

the carb HP 500 and the 500 HP EFI both were 470 hp and the EFI had the E top headers,

nothing special about that EFI set up and MEFI 3 and 1989 Multec fuel injectors, plus bank (batched) fired for making any added power. Wonder if the carb 500 would have made more power than the 500 EFI if it had installed CMI E top headers also ??. I understand they are short runners for the E tops so they give up some but the GILs were not no powerhouse plus they reverted water.

Back in the day I guess it was fairly good but PCM 555 was out in late 2000. If I recall correctly the 500 HP EFI ended at the end of 2003. Maybe early 2004 ??

Wildman_grafix

11-14-2018 07:13 AM

https://cimg4.ibsrv.net/gimg/www.off...373847ff66.jpg
https://cimg9.ibsrv.net/gimg/www.off...ff3b6b2dde.jpg
Here are dyno numbers from totally stock HP500EFI and a stock 525. Same dyno, yes different years but interesting when you look at the curves. I should put into a spreadsheet and make a curve.

Also note this was before the injectors were cleaned and flowed on the 500's.

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