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How many hours are to many on a 496?


How many hours are to many on a 496?

Old 08-31-2015, 11:16 AM
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my mechanic said a 496 should run 1000-1200 with no major issues. But you may start seeing some things go after that. However, I know some people who have seen 2000 hrs on a 454 Merc. Mainly just depends on how it's run and maintained. I have 375 trouble free on my 496.
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Old 08-31-2015, 11:57 AM
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My father has 1200+ on his 2005 Chaparral 255 SSi with w/380 horse 496 mag (non-H.O), mainly cruises about 3500 rpm. He has no plans to do anything until he has issues.
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Old 08-31-2015, 12:15 PM
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How well is the heart beating??

Meaning get a compression test!!!!

That can tell a lot!!
This Cat is trying to keep up with the Big Dogs
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Old 08-31-2015, 12:17 PM
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400 hours on my 496 MAG. Just put plugs in it because it developed a miss. Runs like new again. That is the only thing I've had to do to it other than oil changes and impellers.
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Old 09-01-2015, 07:59 AM
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450 hours on our 2002 496 Mags (non-H.O.). We've had the boat three years now and put about a hundred hours on it.

We've done impellers and oil but nothing else so far. I'll put Raylar plug wires and NGK Iridium plugs in over the winter.

And yep, Raylar is still around as a company but I don't know if they still visit or post here.
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Old 09-01-2015, 12:36 PM
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My old sunny had 745 hours on the 496 HO and it ran flawlessly. Lots and lots of idle hours though. 496s are bulletproof as long as you don't fvck with them.
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Old 09-01-2015, 12:56 PM
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I always thought idle hours were harder on an engine than running some mid range rpms.
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Old 09-01-2015, 03:50 PM
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Indy correct - go idle around a 496 all day and tell me at some point how well the 496 is running ? Then pull out the spark plugs - rich as hell and I seen some that will foul spark plugs during very long periods of idling. the computer programed and the way the positive crank vent system is for the 496 along with if you have the older intake gaskets that were changed I think in 2005 to a much better gasket & design. this helped out with loss of motor oil to. These 3 areas alone really sooted up the transom for some and can foul out the spark plugs .

Post # 6 has correct info for most marine engines.

Last edited by BUP; 09-01-2015 at 04:38 PM.
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Old 09-01-2015, 06:27 PM
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I have read a lot about transom soot and rich condition on a 496, but my 2006 motors don't soot a bit, in fact my muffler inserts weren't even dirty after 25 hours. I also have about 35 hours on this oil change with Mobil 1 15/50 synthetic, running them quite hard at times, and neither engine has used a drop of oil. I don't know if I am lucky or if the incremental upgrades made through the different model years are the reason my motors don't have the issues some have. They are currently at 190 hours.

I know there are plenty of people who look down on these motors compared to the age old 502, but I can find very little not to like about the package. They are smooth, torquey, and dead nuts reliable. Add to that several examples over 1000 hours with no tear downs and it seems to be one of Mercury's better packages.
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Old 09-01-2015, 06:34 PM
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I heard 496's have a tendency to revert water. With that said I am guessing idling is not good. In salt water even worse...I'm willing to bet valves on some of these 496's don't look that great.
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