15/50 Mobil 1. I wasn't on the boat that day so I don't know how hot it got but I'm sure it was cooking!!! Also popped the dipstick.... It was quite a thrashing those poor engines took. The XZ drive I built held up the whole way though! :-)

That's why I've asked.

That is a major sign of either:
Too thin of an oil (can be from dilution or too low of weight)
Too high of oil temps (again causing oil to be too thin)
Windage introducing air into oil and oil not being able to disperse quick enough
Improper oil drainage back into pan for the volume of the pan (this is more typical though on small 4-5 quart pans)

And yes, I've been there before many times.....each time was too hot for the too thin weight oil. You usually know it's coming because the oil psi is slightly lower at high rpm and as coming back to idle the oil psi is a good amt lower than normal.

Believe it or not, this is how I gauge what weight oil is better for the engine + use at hand vs just assuming. If he was say using 15W-40 and the oil was good and not diluted, then time to step up to next higher weight. In this case 15W50 or 20W50. If that doesn't do it, oil temps really need to be looked at.

He was running 15/50 Mobil 1 when it happened. Prior to this event he normally ran Royal Purple. He's going to switch back to the Royal Purple or Amsoil 15/50. Then again, he never ran that long or that hard WOT so it's kind of a crap shoot. I wish I was there, it was a fun trip from the story I heard. lol

Engines are also getting tired and I think he wants me to rebuild them next winter.

Friends don't let friends put purple in their engines. On their engines is okay. LOL.

Hmm, anyone I might know Panther?

Yep! lol

I've ran the High Rpm Morel lifter with 30wt 40wt and 20w50. 0 lash, 1/4 turn 1/2 turn and full turn. Never had any ticking noises from lifters. I usually adjust oil viscosity according to outside temp. Ran up to 60wt with hydraulic lifters (not Morel) during the dog days of summer. I'd never try running that heavy of an oil when it's cold. Motors don't turn over well with heavy wt. oil in cold weather. I've always used HV oil pump in my boat motors 80+ lbs at idle got over 100 running. My personal educated guess at the lifter dilemma is its either got to be to much clearance or oil system delivery. I think you guys are barking up the wrong tree in regards to running 5w30 15w50 or whatever. To many guys running different brands and grades of oil and end up with the same issue with the lifter. Time to look at it from a different perspective.

what part number lifter are you talking about?

Mike what you run for seat pressure typically?

5045 the ones they say not to run any oil thicker than 5w40