I had a friend with a Powerplay ask the same question the other day, comparing his 350 in his boat with the 350 in his pick-up. I used the example of running in the park versus running in the pool, which one is harder to do. Or should I say substantially harder!

Unless it's blue I'd expect to get at least 1500-2000 hours MINIMUM out a bigblock before needing any freshing. Seems most underestimate the duribility of the black bigblock.

Out of 30000 OSO members, I think you'd be lucky to find 20 that own or have owned any Merc gas bbc engines with that many hours.
It just doesn't happen too often without a major failure.

So, your saying OSO members are brutal on their toyz??

Err, wait, never mind....

driving a boat is comparable to driving a car up a 60 degree incline with your foot in the floor and the tach glued to the reline. How long would your car motor last under those conditions?

Take your truck and a 10,000 trailer and pull uphill at 5,000 rpm for its whole life and see how long it lasts !!!!!!!!

Marine engions never get to coast,,,, they are always under heavy load.

Wow.

Real word estimates from my limited experience tell me that if you see over 800 hours on ANY marine engine other than an oil burner you are doing something.

BTW, I have black big blocks. 291 hrs. on one, 287 on the other. (20 years of time though).

I am assuming if I get two more seasons without major overhaul I have done well.
More than likely I will try to get rid of it after this coming summer though.

Your 6.0 is puking coolant because it has a head gasket/bolt problem. You should fix it before you need a whole new motor.

I brought it to Dealership, and wsa told by mechanic that they are having alot of trouble with a internal water cooler that gets stopped up, causing pressure to build up, and causes to puke.

Truck is a 06 model, 6.0, and is supposed to have a improved head gasket from the earlier 6.0's. I have to bring in my truck to have the cooler replaced. He showed me one, have to take the top half of the engine apart to change.

Then again, may be the head gaskets too. I have an Edge programmer, but I always turn it to stock while towing. Only leave it on level 3 for regular driving. Increased fuel mpg by 3.4 mpg.

Mechanic also told me that the new 6.4's have to have the cabs lifted off frame to work on anything major on the engine.

I can imagine how many rattles you will have after having that done at a local dealership