496 MAG post-break-in RPM gain
 

We have about 28 hours on the new ride and have noted an RPM gain of 400-500 RPMs now that we are past our break-in period. Is this amount of RPM gain normal, or is something up? The boat is running great!!!!!

I thought I would gain a little RPM after the engine breaks in, but this is now getting me close to the rev limiter. I was seeing 5100 RPMs this weekend with 2 adults, 4 kids, full fuel, and 80 degrees in the Midwest. The lake was slightly choppy.

Thanks!

I've heard an unconfirmed point that the new ECM/PCM's have a built in break-in period setup to not let you push it too hard. Then older conventional wisdom says as the motor breaks in it loosens up etc. I personally think it's crap. I believe "break-in" period, is Mercruisers way of having you take longer running the boat easy so as to get you to the end of the factory warranty before anything breaks and they have to pay. I believe you can spank'em right out of the boax like anyother newly built high horsepower motors whether it be for boats, cars, trucks, NASCAR, etc.

Then again, I know nuttin' much bout nothin'...:chimp:

I've always been able to hit 4,800 RPM on my 496 MAG from hour one. There has been no increase max RPM even after 135 hours of use.

any factory built motor will loosen up a bit and make a few more revs after break in... its mostly the reduction in internal friction as the rings seat.... yours sounds like a lot more than that but that could be anything systemic...

as for running them flat out straight out of the box, that's just stupid for too many reasons to even write down.

To my knowledge, there is no programming in the Merc PCM555 used on the 496's to hold rpms down under the preset rev-limits in the ECM during break-in. These are Mercruiser engines not Mercury Racing blueprinted engines. these 496 motors come pre-assembled from the Tonawanda , New york GM plant before Mercruiser accessorizes and paints them black. They come from GM on the "tight" side on piston clearances and some are tighter than others so they may loosen up more after some low hour usuage. In no case should a new stock Mercruiser 496 engine be run all out hard at full rpms until it has had a chance to break-in slightly and loosen up a bit. Read the Mercruiser operation booklet delivered with the engine and hopefully given by the boat builder and sales people to the new owner.

Sounds like you got a nice running 496. Take care of it and treat it right and it will take care of you!

Regards,
Ray @ Raylar

I agree with Ray he's right. The drive needs to break in too and it will free up a little like the engine does. As for the extra R's maybe a couple for the chop, a couple because your trimming it different and a couple more cause you got a good one.
Jim

Thanks guys. I did the break in by the book and made sure she was treated right. I have had no issues with a black transom (perfectly clean) and the engine runs and sounds great.

I know there are a lot of variances in the 525s as it relates to HP per engine. Any idea as to the 'range' of HP various 496 Mags might run?

Don't take my comment on hour one literally. It is just a figure of speech similar to saying "from day one". In other words, from the time it is reasonable to run the boat up to WOT. Obvioulsy it is not a smart thing to take a zero hour motor and put the onion to it. I know how to properly break a motor in. But thanks anyway for calling me stupid. :rolleyes:

Naw, I think it was me. I was being exaggeratively flippant and got spanked....:p

Personally I think mine has "lost" rpm since break-in...:eek: :p

You Sunsation guys are all the same! :drink: Mentalpause is exaggeratively flippant when spanked! :eek: