Dazed and Confused?
 

Geez! My glasses must need a prescription update . I read this spec. from Mercru Racing as way less than 5650rpms??
http://www.mercuryracing.com/sterndr...5efi/specs.php.
Guess there must be a lot of different factory programmed ECM's for the 525efi as the three we were working with all went to soft limit at 5350rpms. guess Mercury Racing is playing with us EH!

Best Regards,
Ray @ Raylar

Ray, that link is not working for me.

Edit in after Ray's "follow up" link is now working for me. Thanks.

The link is to Mercury Racing site, sterndrive section, HP525efi engine and click on specs page for that engine. My posted link works great on my computer?

Best Regards,
Ray @ Raylar

Funny, I've read a boat load of PCM's, from early 2001 to current, and I have yet to find one with a 5350 soft limit? The overspeed works like this, there is first a max RPM for warning, meaning buzzer, dash indication for overspeed. Then there is an rpm over that to start to cut cylinders, then there is a overall max rpm where all cylinders are cut to limit rpm.

Therefore, in race boats, and plenty of pleasure boaters can and do run over 5400, even 5550, consistently. I feel very strongly that its better to maintain that rpm, even 5650 and NOT cut cylinders, since that creates far more stress on the rods, crank, balancer, bearings.... then just a consistent and steady RPM.

Interestig read between you two guys that are "in the know" so -to-speak.
I am amazed at how much can be learned from this site.
Thanks to the both of you for your insights.

Dustin:

I understand what you are saying and it sounds like you have run many more 525efi PCM555's than I.
I can just say that obviously Mercury has put a couple of different programming versions out there, as the three we worked with all seemed to start a soft limit cutoff at about 5350rpm and were in full rev-limit mode before 5500rpms. Keep in mind that as you know it is difficult to pinpoint the exact cutout points under load during a full pull and we did not spend a lot of time at these points as I agree with you that loading the engine at these rpms and going on and off rev-limit is hard on the engine and its internals. I think two of the ECM's we have are early units 2002-2003 parts that came of 525's with the front balancer mounted reluctors and such. The other is a 2005 year unit and its obvious from their serializing that they are different versions and also have slightly different program features and programming.
Some of my reasoning here is from our findings, that one, peak power on the two HP525efi's we worked with on the dyno and with the standard stock camshafts occurred at 5200 rpms and even when we raised the rev-limit setting to 5600 rpms , we saw the power falling off above 5300 rpms.
I realize that a lot of racers using HP525efi's are able to run their boats with advantages of running beyond the peak power rpm and gain higher prop speeds and some overall boat speed with the right setups and designs. My point here is that for most non-race recreational performance boats generally this is not something most boats will benefit from, so why go there? and furthur stress the engine and its components, especially when most of these users are looking for maximum relaible engine life hours from their HP525efi before they must freshen and rebuild their engines.
Why does Mercury Racing recommend maximum full throlle rpms be held at 5200 rpms or less? Maybe they were just trying to protect Mercury from warranty claims. In any event the HP525efi engine (less CMI header leak issues) has gained a great reputation for durability and reliability in the last 9 - 10 years. My sources tell me that there are nearly 5000 units sold and put in the marketplace .
I would guess that less than 10% were or are still out there being raced. This probably means that 90% or so of all HP525efi's are out there are being used in recreational performance boating not racing. Just some findings we experienced and reasoning for my opinions.

Best Regards,
Ray @ Raylar

I've followed this one closely. Good read; thanks guys!

This further explains why my prop testing on a twin engine, late model 525 boat (with zero mods) had consistent RPM history readings well above 5450.

I"ve seen quite a few conflicting pieces of info from Mercrury on a number of things so you certainly can't always go by their literature!! If I'm not mistaken, I think I remember the "range" on 3 of these engines going from zero all the way up to 5600 or 5800.

There was a noticeable gap from the max possible compared to what the engines had ever run.. I wondered why that was the case but did not chase it down.

Now I'm gonna go back and read the files. Can't remember exactly.

Cheers! :ernaehrung004:

I can guarantee you that there is not a stock 525HP EFI motor out there with a 5350 limit. Whether internal or external crank sensor, its the same 24x pattern and is very accurate.

You mentioned beyond peak hp rpm, but thats at 5650-5700rpm so thats what were talking about. Power doesn't fall at 5450 or 5500, it keeps climbing.

As for Mercury stating 5200rpm and not going further? They met the HP power criteria, in fact, they surpassed it. There OEM, they meet goals, achieve them and maximize profit off of that. Can that motor RPM higher and survive? Yes, it can. Its not just high production line GM crate engine like the older Mercury motors, its a low volume production motor with H-beam manley rods, ARP rod bolts, JE pistons, Edelbrock heads, crank gold rockers.... Plenty of good pieces that will certainly hold up.

The crankshaft is made by Kellogg http://www.kelloggcrankshaft.com not the standard big blk crank