Well, I have worked thru BOTH engines and have YET to find a broken valve spring on either of these 1999 HP 500 EFIs. After all of the horror stories about broken and deformed springs it is obvious that you would have to beat the hell out of these engines to encounter any problems. I have 577 hours on 'em. The only thing I have found is a rocker arm that was a bit loose. This has been a real pain in the ass project, but I will feel better knowing I got this job done. KUDOS to Mercury Racing for building two awesome engines. No need to F&*) with these, leave them alone, run Amsoil High Perf 20w50 and you are good to go. I would REALLY like to check the old springs for seat pressure, I am thinking they might still be within specs.
Thanks to Teague Custom Marine for GREAT pricing and advice

I had a buddy who ran a set of 1995 HP 500's very hard for over 1000 hours during 5 or 6 seasons with no internal engine repairs. He replaced them when one of them got water contamination in the oil.

The recommendation to replace the valve springs is not a myth and the 500efi springs are not prone to failure like the carbed 500hps.
The 500efi springs just get weak and do not generally break. The head gaskets usually don't last that many hours though.

I think in 09 the 500 hp springs where adressed at the factory, you notice the risers on the gill exhaust are higher than the early ones to help with reversion.

carbed 500s - break springs -
FI 500s - weak springs

Put a spring tester on your old ones. I bet you anything they are weak...but "look" ok.

Just had both of mine done, 2003 HP 500EFI's, 292-Hours, according to the engine builder all the springs were weak, beyond spec. None were broken. He said the head gaskets were shot and if I would have waited another season I probably would have had issues.

YOUTUBE]http://youtu.be/TQxK0T6CEtw[/YOUTUBE]
Runs great but is annoying the hell out of me....any ideas?? This was a preexisting condition from last year but I forgot about till I fired the engines up after the valve spring job. Ran it with the drive removed to eliminate the gimbal bearing, coupler, and drive gear housing from the equation, also removed the serpentine belt to eliminate the alternator, water pump,idler pulley, etc. All Gearheads your comment are appreciated.