I plan to pull the engines out again this winter to do some work in the engine compartment, and plug a hole for the A/C intake.

While out I want to change the cams in the engines.

These are Merc 500 EFI's (2002 Models)

Last year we freshened up the motors and replaced the stock heads with World Merlin II cast heads, and bumped the compression up to 9.1:1.

Tyler Crocket reprogramed the ECM's to add a little more fuel from mid to top end and we raised the rev limiters to 5550 RPM.

Other then that the motors are completely stock.

Some of you have said that I should have changed the cams to take advantage of the better flowing heads.

So now I have the chance to do it.

What is the cam of choice for this application to give me the most performance?

Thanks

Doc,

just out of curiousity, what kind of gains did you see?

How about the HP525EFI camshaft?
Should be worth a good 25-30HP over the 500 cam.
It will work well with the MPI and should be an easy program change.
May not even need a program change???

Which size Merlins did you go with? Are you going to stay with the 5550 as the max rpm?

BB-Chevy Merlin II Cast Iron Cylinder Head
320cc Retangular Intake Ports
119cc Combustion Chambers
2.300'' Int/1.880'' Exh Valves
1.550'' Valve Springs, .650'' Max Lift for Hydraulic Roller Cam


I don't plan to spin it higher than 5300 RPM.

Get cstraub or RNBuilder to cut you a cam.Don't buy off the self cam!!

The next step up on the Crane is 741 it has a lot of overlap and is at 112ls. Even on my blown apli I could of made some more power with a custom cut cam for my motor .But it gave me a little cushion when I put the 10lb pulley on it

Chris or Bob do have the specks on the 525 EFI cam , Wondering what it is????????

As far as the 500 efi and the 525efi. Besides the cam they also change the the heads and headers to get the increased HP.

Doc just go ahead and put you some Whipples on it. With that CR just don't spin it as fast.But the $$$$.


Good luck

Rob

You think the AC pickup might be slowing ya down??

From what I have read in other threads:
The 500EFI cam is basically a Crane 731 ground with a 114°LSA and the 525EFI cam is a 741 with a 114°LSA...

Those big sweeping headers on the 525 have got to be an improvement but, the $$...

I would think you could get pretty close on SOME of the off the shelf cams that are out there to day. Granted there is allways a better grind that can make more power , but 5-10hp? or more?Also differant manf use differant ramp profiles and cam timming. I think i remember the Ultradyne soild race rollers had a very steep ramp that was tuff on valve train,but made some good power

Rob

YES

I have seen a 2-3 MPH increase from boats that had them removed and put on the transom below the water line.

Thanks for the info on the cams.

let me know how that turns out. Ill move mine.