mwdill

THATS INSANE!!!
i would'nt mind finding one that needs a rebuild but then the exhaust would get me.

Pismo10

I am sure the CMI Sport Tube/Big Tube would yield about the same flow and hp for much less $$.

docmanrich37

Bolt pattern is not the same thats what merc wanted.

Linster

The 525 Cam is a 16HR00004 from Crane. (741 on 114).

Elderbrock after market heads for marine use the standard bolt pattern for the exhaust. Standard CMI's will work and you will not need to get them from Merc.

On exhaust there are two rows of bolts, 4 on top, 4 on bottom. On the 525 EFI, the 4 on the bottom are the same as all BBC. The 4 on top Merc moved to the left about 3/8" so you can not use their exhaust on after market heads or their heads with after market exhaust. You can accomplish the 525 conversion with after market parts and do not need to go to Merc. The computer does not know where the exhaust bolts are located.

This is a good conversion if you need a rebuilt, you have been in salt water, and probally need new heads anyway. You get all the benefits of the EFI. Easy starting good idle and better throttle response. Probally wont hurt the resale as well. Do you ever check the exhaust bolts when buying a boat?

The question is on what Elderbrock head to use. The Rectangle port is 118cc and make an 8.75CR. I have been told but never verified, that Merc uses the 110cc semi closed head. It is against all Merc literature so I would have to dig on this issue if I was going to do this.

jryan26

You can re-drill the same flange.

rmbuilder

Docmanrich37,
A word of caution in trying to duplicate the performance of the 525EFI using Edelbrock aftermarket marine heads. The commercially available marine heads from Edelbrock have very little in common with the 525 EFI heads other than they are cast in the same foundry. They Merc pieces are machined in a separate area with the finish work done at Merc Racing. Merc developed a proprietary program specifically for the 525 that is unique to this application. The bare heads can be purchased from Merc racing as part #:
843944A04 Right
843944A05 Left
There are aftermarket heads that are capable of duplicating the 525 EFI output, however the Edelbrock "marine" heads would likely come up well short.
Bob

Dock Holiday

We did it in a round about way, and I am VERY pleased.

Took the stock 500 EFI's and changed the heads to World Merlin II Rect Port heads. Added the Crane 741 cam, bumped the compression slightly to 9.25:1 and Mark Boos at Precision dyno tuned this exact set up at 590 HP and we sent the ECU to him and he reprogramed them and WOW.

It is sweet. I have a buddy doing the exact same set up on his Scarab after seeing our results.

I picked up 6 MPH with this and some minor hull work on a Baja 36 Outlaw.

Pushing 28 pitch labbed props at 5400 RPM with GPS of 78 MPH.

offshoredrillin

whats your hp Dock? JC is doing my 500's and Mark has the comp. I'm really looking forward to it. JC told me the Tiger will be a different beast this year

Dock Holiday

A solid 590HP with the accessories on.

offshoredrillin

nice, I'm running 26 box props now, will look at labbing them and possible some 28 labbed. DPT has a set of 28's already done. I like the real time numbers, if I could hit 80 this year that would be awesome.