K.craig99,
It shouldn't need any of those major internal rebuild items.
I have somewhere in the mid 700 hr's on my 1993 454 that's in my 27ft Chris Craft sport cruiser and it doesn't burn a drop of oil or have any loss of power regarding mph from when it was new and still idles rock smooth steady and quiet, so if what you're looking at has been well maintained looks and runs good I wouldn't worry or bat an eye at 500 hr's or you'll be risking insulting the owner if you try using that to bargain the price since he's to original owner but you're in a better position to determine that.
Remember if you ran your car continuously at 60 mph non-stop for 500 hr's you would only be @ 30,000 miles or 2-1/2 yr's old, of course the average auto/truck runs at about 2000 rpm's @ 60 mph where the average boat engine usually cruises around 3000 rpm's but is not subjected to the same high heat stress a land vehicle is subjected to and so I wouldn't consider 500 hr's high hours until you're in the mid teens.
That's why you should ocean or lake test it once you strike a general deal, just my opinion others may vary.
Good Luck,
WH
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