1 owner, mostly ran between 3000-3200rpm, synthetic oil changed every 25 hours, dont burn any oil...

Ticking bomb? Or good till it starts burning oil?

What do you think about that? Needs rebuild asap? Or run it like that?

The head gaskets should have failed about 6-700 hours ago

I pulled 3 apart this winter with 250-400 very light hours, head gaskets were pushed between cylinders on 2, exhaust valves were pitted/rotted at the stem, valve seats were beat. So yeah she's not ticking she's a grenade with the pin pulled and released

2 of the motors Jamie pulled apart were ours. I was shocked at the condition of the valves. And our motors have pretty gentle use. Also heard from several folks that the stock springs are pretty weak. IMO the boat you are looking will need 3 top to bottom rebuilds if they've never been touched.

That's a pretty good testament to that blue motor, agree rebuild it

so what would typically blow up? head gasket? valve? or even bottom end could break a piston or crank?

Death by head gasket seems to be a 502 specific issue this guy has 3 that surpassed 1000 hours maybe he has closed cooling and the valve spring gods have been smiling upon him

Id be afraid for dropping a valve caused by weak springs, maybe its lasted this far from lower rpm's if it was scanned, spin it to 5K and look out.

The 3 you pulled apart, did they have issues for them to be pulled apart or was this preventive maintenance and discovered the problems?

Must just be people doing things the correct way^^