Here's the latest.

Mechanic can not find any visible signs of damage in the upp er end. He talked to Mer HP and Bob Teague, both have said no problem with valve springs on the HP500EFI, it was a problem with the HP500 carberated engines.

Cams look fine, replacing lifters should have the boat abck by next weekend, will update after I run it.

Thnaks for all the input and advise

That's good news BB, Good for you, NOT SO GOOD for me!
Are they just changing the lifters because they are already in there? Do you know if they, (Merc HP and Teaque) contribute this mainly to the Risers on the GIL manifolds on the Carb HP500's? I kinda hope so, because I have KE manifolds and I don't know of anyone who has a reversion problem with KE's pipes?
Thanks,
MD

Dean Ferry, the issue with the exhaust valve springs as I understand it was that they were breaking at around 150-170 hours. They changed the spring on the EFI models, and on the repair kits from Merc. As far as why they are changing them, that is were everyone feels the knocking is coming from. Not that I am an expert, but when I first heard it it sounded like a lifter.

BB,
Thanks for all the info. If you don't mind, could you please let me know how your rework goes and how much $$?
Thanks,
Md

Just an update, haven't got the bill yet but here's what we found;

Knocking was from a soft lifter, replaced them all no more noise

Oil in bilge was from the front seal in the drive. THis is the strange part, the retaining lock nut on the upper thrust bearing was coming loose on the drive. This was causing the thrust bearing spacer to push the seal out. Simple to fix now, but I have benn told if I had run it much more it would have catostrophically failed the drive.

Only a mechanic who keeps finding things wrong would say I was lucky, but he's right. I caught the lifter noise early enough to not have any other damage and caught the drive early enough to not cause an upper bearing failure.

To all those that provided input into the exhaust valve spring failure, here's what we learned: both Bob Teague and Mercury HP admitted spring failures on the carb'd HP500, they changed the part on the EFI's. It is available as an upgrade for the carb'd 500's.

Thanks to all for your help and assistance:)

Lastest update, knocking returned very quickly (matter of minutes on the water), mechanic took a compression check and found number 7 cylinder down to 40lbs. Pulled the head and found the number 7 piston burned.

Knocking now expected to have been carbon hitting the head.

No final cost yet, but expect it to be steep, and I have lost half my summer.

Hopefully it will be fixed (correctly this time) by this weekend.

Mama tryed, Kenny (aka Wheeler Dealer) and AeroBob thanks for all the rides in the last 6 weeks, with any luck I won't need them any more.

There are many questions as to why this was not found earlier, but live and learn.

For what it is worth, I have now also been told (second hand) that several HP500's have had the number 7 piston go south in our area. :(