How much gain in rpms is normal/average after breaking in a 496HO?

-Craig

Ive always heard they are ready to go out of the box.....you just arent supposed to sustain the high rpms etc for too long

Actually, what I meant to ask was how much will these motors loosen up after they are broke in, as far as rpms?

-Craig

Im not sure if the 496 ECM will artificially restrict top RPM's for a period of time based based on "break in." Will the engine loosen up on its own keeping all variables the same? Again, not sure but i would say no. I think raylar or another 496 guru would know for sure.

Ray has stated in the past there is no break-in algorithm in the ECM. My 496 MAG might have picked up 50 RPM once it loosened up. I'm at 160 hours now.

With my old prop, I was on the rev limiter when it was new. (5000rpm) It might have gotten a bit above that when it was broken in, but the ECU probably kept it close. I didn't re-prop unti lafter break-in, so I can't make that comparison. Current prop only 4800 rpm I went from a 23p 3 blade to 24p 4 blade.

I sort of followed the break-in process of limiting time at WOT until it had 10 hours on it. No mechanical problems since (175 hours), just some electrical gremlins in the wiring harness.

Well here’s what I got going on. Brand new 496HO, mfr date July 2007. I have less than 10 hours on it. I know you’re not suppose to open it WOT until after 10 hours, but what I’ve noticed is I am not able to…..The boat is a 23’, Checkmate, only weighs like 2800lbs. I first ran a 27 Mirage plus, I thought I’d just give her a short burst at full throttle and it would only turn it about 4600rpms. Fine, I thought. I’ll try a 25 Mirage plus….same thing with that, only 4600 rpms. Was expecting to pick up 300-400. Maybe these are fluke props and are actually close to the same pitch? Can’t be…. the 25 Mirage behaved way different, better hole shot, and acceleration, and I can tell just by looking at it that it is different pitch.

FYI CHeckered.

Merc props are actually a half or a whole pitch lower then the specs. A 25" P is actually a 24". You might want to lab the props or see what a Hydro will do. My suggestion is to have them cupped more.

Well I got some guys (and merc dealers) telling me that it will loosen up after 20 hours, and after I change oil as much as 300-400 rpms. (The merc break-in oil is heavier?) Some say not that much, some say maybe none at all. Doesn’t really make sense that it can’t turn the 25p more rpms than the 27p.

My buddy can turn the 25p 4800 rpms with a 4000lb boat and only 496mag/375hp

I can only turn it 4600 rpms with a 2800lb boat and 496HO/425hp.

Maybe I’m just jumping the gun here, and should slow down and wait until break-in is done before I start looking at WOT rpm comparisons.

-Craig

The merc factory oil is the 25/40 quicksilver stuff as far as I know. I think something is up with your engine. No alarms or anything? I have owned 3 496HO's now and none of them had any issue getting up to 4850+ (depending on props), even before 20 hours was up.

There is no "break-in" feature of the ECM (at least not any of the motors I've owned). I would hook it to a scanner if you have access, just to check for codes. 4600 is right around 90% of rev limiter, which could be one of the "limp" modes of the ECM. However, normally, you would get an audible alarm along with it, I believe. Only way to know for certain is a scanner.