How long can a 496 last? How about this!
 

http://seattle.craigslist.org/see/boa/2977084923.html

Here's a copy of the ad

Description of item #2:

1 engine and 1 out drive described as follows:

2007 Mercruiser 496 (375hp) DTS Mercury engines with 2009 Mercury Bravo 3 X drives 1.81 ratio. Engine was previously used in Police patrol vessel and has approx. 2280 hrs on it. Engine has been regularly maintained by certified mechanics and is in good working condition and is free of any known mechanical issues. (Engines and drive are due for routine service at this time) Maintenance records are available upon request. Outdrive has approx. 660 hrs on it and has also been regularly maintained. Both items are sold together and used in as-is condition with no warranty.

Engine hours 2280

DTS Controls not included.

We have had commercial clients with over 3000hrs on properly maintained and heavily used 496's. EFI losed cooling engines will run and run.

Best Regards,
Ray @ Raylar

Commercial and fleet vehicle engines last a long time due to a couple of reasons... 1) Regular maintenance 2) They spend a good deal of their lives running... As in fluids are circulating, seals are staying wet, parts are getting lubed. Wear and tear is inevitable, so at some point an overhaul is needed. I actually worry more when I look at a boat with seriously low hours as apposed to a boat that has decent hours with service paperwork. Rob

the one in a Towboats US boat here in North Georgia was just replaced with around 5000 hours. it was still running fine but he got worried with that many hours so they put in a new one.

my 35 and 38 sonic charter boats averaged 2 yrs and 3 thousand hrs before we took them out and sold them. our bravos wernt so lucky!