Seriously does anyone know if there is anything behind or a cause for seeing so many issues with these engines?

I continually see problems on the net, and even have a whole hp500 in my garage (in parts of course lol) waiting on getting rebuilt.

In talking with some certified (different than certifiable?? lol) Merc techs I get totally different answers. I have heard the stories about reversion from the larger cams, sensitivity to lean or rich conditions, issues about exhaust heights and length, and pretty much anything else you can think of, but could there be more to it than owners messing up??

The one I have supposedly had problems from the exhaust, but low and behold there are no problems with the same exhaust on the replacement.

Any input would be appreciated.

Let somebody turn you on and run the piss out of you all day and see how long you last!

Valve seats are one issue I know of with these motors

hp500's were just cheaply manufactured, plain and simple. Time to call a spade, a spade. They "seem" to have the most issues consistently than any other motor type, not including high horse 'droid engines.

There are a lot of old stick 502's running around out there with over a 1000 hours. They're good motors I think, and they will treat you like you treat them.

I agree with Recklesss on the 502s. I guess I'm not seeing the issues with these you speak of. I know mine treated me very well.

Buck

about 2-3 hours straight By then the oil is burned up and the piston scratches the wall

Seriously (sorta)...this is my first summer on OSO, and I wonder if it's just the seasonal return to operation that all these "problems" come out of the woodwork. Look at the string of overheating threads that popped up the last month and a half.

502's a great motor ... 500HP is just that ... a high HP motor ...High HP motors break ...by that I mean if you dont go thru a HP motor at say 250-300 hrs you asking for it ...esp the valve train ....

Its a given that the most popular Merc HP engines will have the most stories told about problems with them. There are so many out there with a lot of hours that you never here about. There are a ton of factors that contribute to problems. The main ones being driving style and maintenance. Maintenance can include internal engine parts as well. The valve train is the issue in all HP stuff.

Had 289 hours on my HP500 carb motor when I sold the boat. Loved it. Not one issue.

HAD 653 hrs on my 502 mag efi
the previous owner put a 7# whipple on it after 100 hrs.
boat finally blew a head gaskket between # 5&7.
engine builder torn it down and inspected it and everything was great except the gasket. I heard of them leaking on teh rear of the intake gasket causing a lean condition. usually when the gasket gets OLD and dried out.
Keep the motor oil cool and drive it. friend got over 800 hrs on his stock 502 mag efi.