Originally Posted by Whipple Charged

Actually that motor has no problem making 575hp. Most stock motors make 540-550hp out of the box. The stock intake will support more than 575hp. With light porting, bigger camshaft, a bump in compression, 615-625hp is achievable. A light port on the intake for port matching will also help. Just had a customer build 2 a few weeks ago. 1 made 621, the other made 630 (5550rpm), both on 91 octane. Both made 624 lbs/trq @ 4100.

Originally Posted by Whipple Charged

Actually that motor has no problem making 575hp. Most stock motors make 540-550hp out of the box. The stock intake will support more than 575hp. With light porting, bigger camshaft, a bump in compression, 615-625hp is achievable. A light port on the intake for port matching will also help. Just had a customer build 2 a few weeks ago. 1 made 621, the other made 630 (5550rpm), both on 91 octane. Both made 624 lbs/trq @ 4100.

Originally Posted by Cole-One

REMEDY I picked up on your old post I'm rebuilding my 525's and it looks like you have be down this road can you point me in the right direction.

Originally Posted by 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

Originally Posted by Cole-One

Thanks for the heads up, I hate to go through all the trouble of rebuilds and come next season hit the keys and run the same which isnt bad but it would be nice to see a extra 2-3 mph.