F350 cracked piston

[TownsendsFJR1300]

That "scruff" section just below the oil ring, where the piston is apparently indexed to clear the crankshaft. Are there any marks on the crank (when the piston is closest to the crank)?

Also, I realize the rings are out of the cylinder but the end gaps look huge. Can you slip the compression rings back in the cylinder to see if your missing part of one-As something WAS imbedded in the top of piston. That lil piece looked like a piece of a piston ring.

Cylinder look ok?

Plus one on lots of carbon where the rings reside. Do they rotate easily in the piston groove(W/O cleaning) or pretty much stuck?

[boscoe99]

Fuel line size caused only one cylinder to run lean?? Kind of doubt it, I don't doubt the running lean, that seems like what happened, but it's more likely something unique to that cylinder.

A bit hotter than the others perhaps?

[boscoe99]

What was the octane rating for the gasoline that was being used? Old gasoline or clean and fresh?

Do you know what was the WOT RPM with the boat loaded before this all happened?

[boscoe99]

Cracked all the way trough on one side

Think of a plate that is positioned upon a wooden dowel.

Pressure is applied to the plate all around. Or rather pressure is applied on the plate just above where the plate rests on the dowel. Then pressure is applied to the plate 90 degrees from where the dowel is.

The plate will crack in line with the wooden dowel. Just like your piston is cracked.

[Jokern]

That "scruff" section just below the oil ring, where the piston is apparently indexed to clear the crankshaft. Are there any marks on the crank (when the piston is closest to the crank)?

Also, I realize the rings are out of the cylinder but the end gaps look huge. Can you slip the compression rings back in the cylinder to see if your missing part of one-As something WAS imbedded in the top of piston. That lil piece looked like a piece of a piston ring.

Cylinder look ok?

Plus one on lots of carbon where the rings reside. Do they rotate easily in the piston groove(W/O cleaning) or pretty much stuck?

Marks on the crank? like piston hits crank?
Next step is to check piston rings in cylinder .

[Jokern]

What was the octane rating for the gasoline that was being used? Old gasoline or clean and fresh?

Do you know what was the WOT RPM with the boat loaded before this all happened?

98 octane.
Clean gas, 30ft. RIB with 12 pass about 5400 rpm when its happened.
Had noticed a slight oilpressure drop when letting off throttle, but it got back to normal after a sec or two

[Jokern]

if it was not stuck there, was it just laying there?
it sure looked like it was stuck.
what was it made of?
aluminum or some other metal.
definitely looks machined

I was maybe a bit hasty cleaning the piston so the bit got lost.