470 hours valve springs and lifters at approx 300 hours. the engines burn maybe 1 qt of oil in 20 hours. did a leak down test at around 400 hours and everything was good. i expect a total of 550 to 600 when i freshen them. probably do some upgrades short of blowers

I had a HP500 in my 29 Fountain and when I sold it, it had 250 or so hours on it. The guy I sold it to ran it for some more hours and then tore it down to change it over to a blower motor. He told me the engine looked like new inside, everything was in perfect shape, springs, valves, bearing, cam and crank shaft, water cooling passages showed no signs of salt water and this had to be clase to 300hrs and all in salt water.
During my time of ownership I changed over to Mobil 1 synth oil at 20hrs and changed the oil every 30-40hrs which for me was around 4 times a year. I also flushed with Salt-A-Way every time or at least every other time.I changed plugs and distruiber cap and rotor every season.
Enjoy your HP500's, they are great engines!
Mike

By the time its a 572, I should be into it for another 12 grand or so I figure.


PS, I pulled the heads at 250 hrs and there were 9 cracks between the valve seats spread between two heads. I swapped them out for the edelbrock marine aluminum heads at that time. New lifters, springs, retasiners, keepers and rocker arms.

A buddy of mine has a Checkmate with a hp500- In the owners manual it quoted that the engine was "built to run at or near full throtlle for 500 hours" -pretty cool statement. I think he is at about 400hrs. I know he does not have the power he used to have, and is thinking rebuild as well. I've noticed Mercury has a rebuildd program now. Might be worth considering. I'd bet it is pricey, but can't imagine anyone knowing the motor better. and it may come back to you with a warranty.

Bob and Shari Smallwood have over 700 hours on their 37AT with HP500s. (I think they are EFIs.) I know Bob runs the boat REALLY easy, and I don't know if he has had them freshened, but that is a testament in itself. (Mostly salt-water as well.)

they are in a 30 ft Hallett that weighs about 8000 lbs.