Can anyone tell by this picture if this is really a 525?

It may be a 525 but not a mercury racing 525

Merc 525's use a distributorless ignition as far as I know and that engine has a distributor.

maybe its a 500 efi ?

that manifold has been around since early / mid 90's from Arizona Speed and Marine

that manifold has been around since early / mid 90's from Arizona Speed and Marine. I always get nervous when I see altered factory looks.

Definately not a Merc 525EFI or 500EFI. It has the same Intake(made by ASM), but that looks to be about it. Imco exhaust and has older style Merc remote oil filter

That is Keith's (Silverback) old Donzi ZX. He did a lot of work on it and it ran over 100 mph. I don't know if that is the same engine but the ad says that the boat has water/flood damage. Here is the ad: http://www.copart.com/c2/individualL...Type=onSaleNow And here is the build thread: http://www.donzi.net/forums/showthre...h-A-Pad-Bottom

Looks like a centrifugal blower on it, unusual mounting of it but definitely looks like a blower of some sort.

Yes, it's blown and was making over 800 hp last I knew.