To frame up this question, Im talking about Mercruiser BBC Black motors. (454, 496, 502)

STOCK, never opened up. But well maintained. (As that is all I would consider)

What do all you consider "A lot" of hours on a used boat engine?

300, 400, 500, 600?

400 is a lot, but I have seen boats for sale with 600!!!

Depends on the age, 300 hours on a 10 year old motor isn't bad. 30 hours a year for example however 300 hours on a 2 year old motor is bad

black engines will last quite a while if properly maintained and they weren't ragged on.

before rebuilds 1000 hours isn't uncommon. Performance boats maybe 800.

How is it bad? Regular use is better than letting it sit and use it every so often.

With proper maintenance those engines should go 1000hrs.

Depends on how those hrs were spent..........wot -redlined or crusin' i'd think.

I looked up the lifespan of stock power on other forums. From what I have found is most stock motors die an early death from overheating or water ingestion, both usually from bad manifolds. There are claims on iboats.com of black motors making it to 3000hrs over there. My motor has 560hrs on it and runs like a watch.

If you want a 2 year old motor that has 300 hours than more power to you! I don't. A diesel powered truck may last a million miles if properly maintained but who would buy a 2 year old truck with 300,000 miles?

My truck monitors how many gallons of fuel it has consumed. If you could get that on a boat, then you would be able to determine if 300 hours in 2 years was bad. IMO... hour meters are useless by themselves. Since you don't have "gallons of fuel consumed" you have to use other indicators, such as the condition of the hull. How clean is the boat inside and out. Do all the accessories work. How clean is the bilge? etc. Hour meters alone... no indication of how much torture the motors have seen.

I think this is the biggest criteria.

I've got a bud with nearly 2000 on a carbed 454 at 17 years old. I'd bet no more than 50 were at redline, the rest cruising.
His last compression and leakdown were still spectacular.
I completely agree with the usage staying regular and not lots of downtime between taking it out on the water.
His thoughts are like its comparable to a truck with 100k miles and he feels that he should make 3-4000.
My 525 SC's have 550 and still have great comp and leakdown. One member posted years ago that Merc racing benched tested this package for 1000hrs with rpm's between 3500 and 5000 during testing!!!
I however am as nervous as a schoolgirl on prom night.
I wouldn't sweat the right boat with 1000, just make sure and survey the engines with a comp and leakdown test.

Happy new years eve, remember to keep it safe!!!

See ya,
Kelly