I'm looking for some feedback on this engine regarding reliability. I'm looking at a 2002 PQ Legend and see some mixed reviews about this engine. 250 hours. Thanks.

Non-HO I believe.

I'm going on my second season with my boat, which has stock twin 496HO Merc's, and have not had any issues. Those engines have been running great and sound even better. I've heard once you start modifying them that they tend to have issues, but I don't know if there's any truth behind that or not.

If you have a survey done on the boat ask the suveryor to give you a print out of the engine performance since new. My surveyor did this and it was very useful info. It shows how long the engine has run at a certain RPM and speed. It was nice to see that my boat had very few hours where she ran above 4500RPM's. The average was around 3k RPM's. This way you can tell if the engines were ran hard. Not sure about other engine types, but I know the 496 engines have the capapability to perform this check.

800 hours is common on these motors.

If you are considering purchase of a boat with 496s or ANY other boat with SmartCraft capabilities...

I highly recommend buying yourself a Rinda scanner or the software for your laptop. It's worth it's weight in gold IMHO for knowing everything about your engine and it's systems.
Rinda Technologies marine diagnostic tools, marine diagnostics, marine scan tools, marine engine software

Sensors like the IAC, Crank and Throttle Position, Water Pressure; etc. etc. will all throw the computer into a tizzy if there is an issue; but it's normally just a bad sensor.

So SmartCraft is basically a recorder of engine peformance history?

And do all 496 engines have the closed cooling? I guess I don't understand that. Why have closed cooling and still pull raw water.

you need to pull the lake water to cool off the heat exchanger or else he coolant would over heat..,kind like air going thrue your radiator to cool the engine coolant in your car

SmartCraft is the brand name of Mercury engine computer management technology. It's the equivalent of the OBD2 & check engine light for your car.

All 496s have closed cooling. They pick up sea water though the drive, and as described above they use a heat exchanger to cool the antifreeze which is cycling through the block. (Much like your car uses air to cool the antifreeze.)

Right I understand but why not just use the lake water and simplify the system? What is the added benefit of having coolant? Does this engine still have the impeller issues that other PQs have?

Not a big deal for a lake boater on fresh water, but it's a huge deal for those other kind of boaters: salt water

And yes, they use virtually the same SWP system as an open cooling system. You have an impeller on the lower starboard side of the engine for the sea water. You also have a traditional water pump on the front of the motor that circulates the antifreeze.