496HO vs 525
 

I'm considering moving up to one of the fountain 35s or 33 and am weighing the advantages of each engine package. Besides the hp difference, what costs and benefits do each offer. I've read that the 496s have cast internals and can not handle extended wot operation, but that the 525s require more regular maintenance. Also, how does the quality of the 496 compare to the old 502/454 MAG MPI. I'm a recreational boater but like to run hard on occasion and don't want premature failure. Would appreciate some real world advice. Thanks

In stock form the 496 is a great platform that will give you hundreds of hours of trouble free boating with basic maintance. Even extended WOT runs are really not a concern.

The 525 is a great motor and puts out alot more power. It will cost more .....alot more and will need valve adjustment and head work around 350 hours. The older 525s had some header leaking issues. The 496s run great as a stock platform and will be cheaper to buy, operate, and insure. How fast do you want to spend is the question as always

While I don't have either I am in the same position as you and have given this much thought.The 496 is a great motor and while some will disagree it seems that if left stock are very reliable.The 525 is a better motor but are very prone to header leaks.In my opinion the only way to fix is to re drill the heads and use manifolds unless you want to test your headers every 20 hours and replace every few years.
I still don't know what I want but I wish there was a bolt on manifold for the 525.

I can't speak 4 the 496's other than I know people w/ them & have not heard them say much of issues w/ them! I can speak 4 my trip 525's & how flawless they have been! good luck!

I had both motors in the same type of hull.
2002 Avanti with 496 Ho mags and now the 2008 Avanti with 525's.
First, the 496's had header problems as well. The CMI headers or the Merc headers are almost identical and similar issues. You hear more about the 525's since most of the 496 headers were STD Merc, and not CMI headers. Only some had the CMI headers. (ALL CMI headers had and have issues, but thats a different topic.)
For the $ the 496 are great and reliable. If you need more HP and more speed 525 is the best choice, with out going to blowers. On the same hull the 525's gave me about 12-15 MPH, but the additional cost you have to justify for your self.
525's need more maintainence but you can run them harder and higher RPM's
(Not sure of the tech data, but I think the 525 rev lim is set at 5400 and the 496 is to 5150+-) So more time on higher RPM's more TLC required.
Knowing what I know now, dealing with Merc. Racing and CMI with different issues... well...uhm.. to not satisfactory results, I would build a reliable standard carbed 502 with 600+ HP's and just forget about all the electronics and computer stuff that Merc. offers, for half the price. I got the Merc 525's when I built the 08 Avanti for the national warranty and the smart craft system, electronics, blue color, etc. At the end of the day it's not worth it. Few shops really know what they are doing anyway so having a "non Merc." motor out ways the cost for the name.
All that being said, I am very happy with the 525's and I had it dinod at 580HP and 581. If you have a near by Marine facility with a good rep on 496's AND 525's fine. If not.. go with a standard 502 carb with more HP, less $.
My .02

PS; neither my 496's or the 525's had any major issues. (aside from the headers, and I have that pretty much figured out.. :) )

It's nice to hear the 496s hold up. I love the look and sound of the blue motors but am afraid of the total cost over its life compared to the 496s. I average 100 hrs/year in the Great Lakes area and want turn key reliability and ease of having them serviced when problems occur. There are some good deals out there on Fountains with both packages, and I really appreciate your input.

The 496 motor definitely hold up. I have a friend of mine who has put 850 hours on his and it has yet to give him one problem in 8+ years of use. They are extremely reliable if left stock.

525's
Great Motor trouble free 210 Hrs.
Can't speak for the 496's.

525: Dropped a valve at 172 hours resulting in a complete rebuild. Now it's 509 cubic inches...... Mechanic hear some chatter and I should have done something about it but live and learn.....

I went through the same decision process last year. My choices were the 33 or 35 Fountain or the 32 Sunsation. I went with the 496 due to cost and turn key reliability. Mine have been great so far!

496s' for sure. Hav an aquaintance that runs the snot out of his at WOT everywhere and if they can last under that idiots throttle hand they are just about bullet proof. There will always b someone faster and like Paradox stated if you want more power have something less complex built than the 525. I guess it depends, as always, how much you got and how much you want to spend

Had the 496 in my Nordic for three years, started every time (that alone is priceless), ran great, little maintenance. Doesn't have the bling & bark of the 525 but the price difference was too much for us at the time. Those CMI issues with the 525 have stung a few that I know.

525. They have turn key reliability too.That's what you are paying so much money for. A head rebuild after 250 hours or so is not that big a deal. It's probably due to the fact that the 525 has the most radical cam of all the Merc Racing engines since it is the only N/A one. It's also why it sounds so good :). BTW, putting manifolds on a 525 would ruin it as it needs long tube headers to scavange exhaust and make it breathe.

I've owned a 496 and now own a 525. Both are great motors. The only downside of the 525 I see is the price.

Lots of posts in the tech section about alarms on both motors. If you are going to own either motor, do yourself a favor and buy a scan tool or diag software. Most of the issues are easy to diagnose and fix. Also, I think smartcraft is pretty good. I have it on my 525, didn't have it on the 496.

What is the average cost to service the 525 heads (at 250 hrs) and does the engine need to be pulled for this? I would think the staggered configuration in the 2007+ 35 Lightnings might make it easier to work on.

It isn't all that cheap to do the 500 or 525 top end. The parts are expensive. Start looking up just the parts and you'll get a good idea. Springs, cam, etc.

"reliable" is a relative term. The 496 should be a reliable 800+ hour engine. The 525 will need the BS done. basically, if you want to go faster you gotta pay.

I have the 496 mag in my 2005 25 Outlaw. 250 hours so far without one issue with the engine. Starts every time and has never left me a day without boating. I have owned it since new.

Twin 525's in the '05 42. One header leaked at 109 hrs without engine damage. Sent it back to CMI who fixed and pressure tested it free. No problems since. Change oil every 25 hours. Keep engines sprayed down with Corrosion X (red can). I have had absolutely trouble free turn key operation to 309 hrs. Not one cent spent on repairs (other than the header).

Whats the header issue on the 525? At the gasket? Im looking at a pair of 2007's with 96 hours on them......I want to move up from 496HO to 525, but all this reading is making me nervous.....

Long story short:
The main issue is with the Mercury spec'd headers on the 525EFIs.
CMI submitted their header for the OEM package.
Mercury wanted something different. (read: cheaper)
CMI built what Mercury asked for.
Mercury 525EFIs are now know for leaky header issues. especially (but NOT exclusively) to boats with staggered engines, as the forward mounted engine allows for more tailpipe & header vibration. The vibrations over time cause the cracks.

They leak water internally and it winds up in the cylinder.

I have a 2005 525EFI. I just replaced the CMI's with Stainless Marine at 230 hrs mainly to be proactive.

The shop that did the work pressure tested the CMI's and said they DID NOT leak.

Maybe I was lucky? I did the Merc service bulletin that eliminates the bypass hoses between the distribution rail and the tails. Also, I always drained them when not in use. They where run in a mix of fresh and salt.

yikes! Was that a problem in 2007? Purely freshwater use.