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Who can do pcm555 ecu tuning? Has anyone done any porting on the 525efi heads and was it enough to require a change to the ecu? 525 seems to be plenty rich and im wondering if a change would be necessary. Also thinking about higher ratio rockers maybe 1.8 or 1.85.

CB-BLR

Talk to Dustin Whipple.

He re-programs the 555PCM and has a porting program for the 525, 600, 662, and 700 Heads... being that they are all the same.

Chris

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Thanks. Anyone done this?

thirdchildhood

iTrader: (6)

It is my understanding that the 525 has the most radical cam of all the Mercury Racing engines being that it is the only naturally aspirated one. It seems to me that increasing valve lift, especially with higher ratio rockers, would be flirting with disaster. Also, since these are the same heads as used on the 700 SCI, I doubt you would see much difference from porting them on a 525.

Raylar

If you want to upgrade a Mercury Racing HP525efi, you need to be careful. Unless someone knows what their doing with cylinder head porting you could damage the engine easily beyond reasonable repair and cause a lot of grief.

We developed and new CNC version with better valve sizes and gear for the Mercury head that we are going to be using on our new HP675efi version of this engine and we have easily dynoed on an independant dyno to 675 horsepower. This can only be accomplished with the engine going up to a 540 cubic inch version (THERE IS NO REPLACEMENT FOR DISPLACEMENT IN A MARINE NA ENGINE!) and with our new CNC'd heads, intake manifold , camshaft profile and our custom reprogramming of the ECM.

The stock HP525efi intake will not flow enough air to support more than about 575HP and the stock 502 cubic inches and stock heads and cam will not flow enough air to support more than that. Remember a stock HP525efi engine already makes 540-550HP at the crankshaft!

If you tried to put a bigger camshaft in the stock HP525efi engine you will end up with serious reversion issues.
Just redoing head work and reprogramming the ECM will not net any real addtional power on a HP525efi as the program from Mercury Racing is a good one and there is no hidden power in the program.

A lot of people in the performance boating community always ask how does Raylar know what its talking about? Its because we do expensive, extensive engineering, development and testing to verify what works and what does not. Raylar tries very hard to make sure what we tend to say and do is based on fact not conjecture.

Old Chinese Proverb say "When in Doubt, Check It Out!"

If you have a HP525efi engine and you want to have Raylar rework it up to our HP675efi, call and let us know. Raylar is starting the production of this engine package in September.

You can read more detail on the thread here on OSO by Matt Truillo titled "Raylar"s new HP525efi package"

Best Regards,
Ray @ Raylar

Wahoo ATV

I know of 8 of them in OPA making more than 575hp with stock intakes, cams and ported stock heads.

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Thank-you Raylar... I have no doubt about your package however that is not what I'm looking for. I have to pull the engines and heads off of them to take care of some other issues. I am a professional engine builder by trade and cylinder head porter with over 20 years experience. While I am no longer in the engine business full time I still do a lot of porting and work for a prominent NHRA engine builder. We have many national records. I have done several sets of these castings and there is some room for improvement in them. I just would like gain a little while they are off. Prob install new pacalloy springs and just a general freshen up. If any can give me any advice or help with the ecm end I would appreciate it. This is a different system and I don't have the stuff to access it. I have a dyno and have tuned many systems in the past.

outriggers

[QUOTE=Raylar;3185967]



The stock HP525efi intake will not flow enough air to support more than about 575HP and the stock 502 cubic inches and stock heads and cam will not flow enough air to issues.
Just redoing head work and reprogramming the ECM will not net any real addtional power on a HP525efi as the program from Mercury Racing is a good one and there is no hidden power in the program. Ray, I like what your doing but I think your a little low at 575 with a stock intake. As far as the ECM Dustin summmed this up pretty well. http://www.offshoreonly.com/forums/g...i-upgrade.html Doug

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[QUOTE=outriggers;3186837]
Outriggers...Clear your message box! LOL

outriggers

Sorry, Done.