ok this thread is just one for future curiosity. I always see Merc 500 and 525 set ups for sale in the swap and wondered what it would take to replicate the EFI's long block. I am assuming the intakes are relatively similar with the aluminum heads being the diff between the two. What would be the punch list for the long block to be as close to Merc specs or what needs improvement from OEM

heads
valves
springs
block
crank
cam
rods
pistons
???

Dave, the money isn't in the long block on the 525's, the most expensive part of duplicating that engine would be all of the accessories: distributorless EFI system, smartcraft, closed cooling, pulleys, brackets, etc.....

I understand that, I would think it could be done as a stand alone system and much of those parts arent hard to find if ya dig enough. Dont need smartcraft or closed cooling. I would think earlier systems could be done as a stand alone, maybe even use a newer aftermarket ecm. I see complete manifold/harness/fuel pump/etc in the fifteen hundred range every so often.

I just did two of them, bought 2 take offs. Got the compleat systems with computers for 2300 @.
You can build anything you want, then use the 525 efi sensors, ignition, intake and throttle body.
Just need to send a build sheet along with the computers to Dustin, and he will program them.
One word of caution from him is to keep the c/r 9.3 or under. I used all my brackets and acc. off my HP500's
Just needed to make spacers so all pulleys would line up and clear the crank trigger.

Raw blocks are CNC machined by Mercury.

I'm curious what it would take to turn one of those Volvo penta intake assy from their5e asm hp efi set up sure looks similar and go doesn't use the cheap stuff Volvo penta doesn't use the cheap stuff phone making this hard on me .

Much easier and less expensive to build a hopped up 500EFI clone.

502 GM Block
GM Rect port heads with some port work and Manley valves
Use a 500EFI intake and MEFI 4
GM forged crank
Manley rods
JE Pistons
Cam similar to a 525EFI cam(Crane 741 on a 114 lob sep) and matching springs
I would work with Bob M and duplicate something he has already spec'd and something that somebody already has an ECM tune for.

I would not use 525EFI heads as it limits the exhaust you can use and increases the price.
You could go to Dart Pro 1 heads or AFR's to boost the HP some more.
The 500efi intake is only good to about 600hp before it becomes a limiting factor.

The most we could get out of the 525 intake was 670hp, it just wouldn't flow past 5800 rpm. We ended up having Wilson build us one.

I agree with Griff, I to would stay away from the merc 525EFI heads/exhaust...more of a pain than anything else when you need to replace either...

I agree, in our build the only things we used was the computer, all the sensors, wiring harness, ignition, and their throttle body.
A 565 cu in, 750hp efi with smart craft and the protection of guardian mode![ATTACH=CONFIG]520992[/ATTACH]