For the used high performance boats, when are there too many hours (assuming boat was run hard) and need to just move on and look at another boat ?

In reading the different threads, it looks like the stock 454's hold up well to 300 hours, the 496's need to be rebuilt after 250 hours, the 502's/525's need valve springs replaced after 225-250 hours, is this correct ?

If the engine is super-charged, I know that this shortens engine life, but by how much 25%, 50%, etc., ?

WE have over 225 hrs on our Rudy Dryden built ICE injected 1300+ hp blown power and have yet to remove our valve covers. We twist these hydraulic roller mills up past 6500 rpms every weekend.We hope to see 300 hrs before a freshen up.

It all depends on the builder, components used,tune up, vigilant oil /water temps,oil change durations as well as luck.

thanks,

I was more referring to the stock motors that probably most of the performance boats have when bought off the show room floor.

a stock 454 will run 1000 + hours,,,, not 300 if serviced correctly

Stock 496's should go 500 hrs before a valve job and 1000 before the bottom end needs rebuiding. a Hp 500 or 525 should go 300 or 400 before a valve job and 600 to 800 before the bottom needs rebuilding. Of course some people can break a bowling ball in a sandbox with their bare hands.

some people can break a bowling ball in a sandbox with their bare hands.
Hey mmmmm c'mon now it was just that 1 time .LMAO

I'm a total freak on the importance of the oil type and frequency of oil changes. You can get well over 500 hrs on stock big blocks (454, 502, 525). My previous boat had 900 hrs with minimal compression loss. We burn Shaffer 20W-50 synthetics and change oil every 30-40 hrs. Many Sprint cars are running the same oil with great results. It's the best keep secret.

Stock 454, and 502 go into the 1000's. We have 670 with good compression numbers. Knock on wood.

I get 250 to 300 hours out of my ProCahrged 454 and run tuff most of the time 720 HP. I change oil at the first sign of consumption. Typically every 18 to 20 hours. 50W Valvoline Racing Oil.

I don't know what threads you're looking at

Stock 454/502 mags are good to around 1000 hrs. Maybe a valve job and springs at 500hrs.

The newer 496HO and HO mags are the same way.

500efis and 525EFI's will need valve springs in the 250-300 hr range and possibly rebuilds in the 500-600hr range.