Gentlemen I am looking at an 01 with 496 Mags 475 hrs one owner boat OR 00 502 MPI 300 hours. I do not intend to modify engines and I am most interested in reliability and cost of ownership. I would love to hear yall’s thoughts on why one might be preferable given my priorities. I should add that we like to cruise the ICW as well as lakes and the 496 mags have closed loop cooling.

502s.

Less sensors to go bad, no antifreeze, no water pump wear issues.

no question, 502's

Would it make a difference if you wanted to cruise salt water and the 496 mags had closed loop cooling?

Not to me it wouldn't. You can install closed cooling on the 502's, but if you flush it well after use, they will last a long time

I'd pick the boat you like best. Both are good motors.

Thanks to those who took time to reply.

First of all, they're 20 year old engines, maintenance is going to be priority one, if you can get records or feel confident on how they were maintained it would help with the decision. I've had both, they were both great engines, get the boat you want and get them checked out, even though the hours are low they're still old and will need to be looked at first.

There's plenty of 1000+ hour 496s running around. They are quite reliable if left stock. At the time of development of the 496 platform, it was the only big block to ever make it through to the end of Mercury's full throttle endurance tests. (I think that's a few hundred hours at full throttle.)

If you plan on modifying it at all, I'd go with the 502. There's lots more aftermarket parts available for the 502. It's a great engine platform with lots of interchangeable parts.

So, go for the one that looks to be better cared for and hopefully that's the one you like the most.

300 continuous hours at Wide Open Throttle was the achievement - GM's test, not Merc's, as far as I know.