Help diagnosing marks on piston + cylinder head

[aok47]

Hi there,
I pulled off the cylinder heads to clean water jackets due to suspected excessive salt/gunge buildup which may be the root cause of my overheat problem and discovered the following on portside #2 piston/ cylinder head.
video showing port side piston and cylinder head markings
cylinder head:

Piston head:



Is this just a hot spot or something more sinister?
First time exploring the cylinder head/piston area so not sure if i just give it a light sand with wet and dry before installing new head gasket, anything else i should do? should i try and get the carbon off the piston with some sort of product?
Appreciate your help guys
AK

 

[racerone]

You need to take this motor apart for inspection.----The marks were made by a broken piston ring , crankshaft sealing ring or broken bearing !!

 

[aok47]

You need to take this motor apart for inspection.----The marks were made by a broken piston ring , crankshaft sealing ring or broken bearing !!

I've had the boat out and motor seemed to be running fine through full range of RPM over a number of hours, I would've been none the wiser had i not taken off the cylinder head as i was looking for source of overheat.

Apologies if this is a stupid question,... with the potential damage you described would you expect the motor to still be running?

Many thanks
AK

 

[racerone]

Hope is eternal.----You have major internal issues based on your pictures.-----You appear to doubt this diagnosis.---------That is not unusual for folks working on their first motor !----Sorry to be blunt.----It is not what you wanted to hear I guess.

 

[aok47]

Hope is eternal.----You have major internal issues based on your pictures.-----You appear to doubt this diagnosis.---------That is not unusual for folks working on their first motor !----Sorry to be blunt.----It is not what you wanted to hear I guess.

All good! Not trying to doubt the diagnosis... I must've mistakedly assumed that the type of issues you pointed out would result in an immediate catastrophic failure if the motor has been running @5000RPM for periods of 30mins at a time.
Count myself lucky to have made it back to the dock!

 

[racerone]

I get blisters on my fingers and tongue trying to explain some of this stuff to folks.-----Post some pictures when you have that 130 HP motor apart !!

 

[F_R]

Agreed, something has busted internally. It will only get worse if you continue to run it. Even to the point of total destruction.

 

[racerone]

My guess ---knowing some motors , that on that big block 90 degree looper it is a crankshaft sealing ring.-----But only a semi educated guess.----I believe there were earlier posts discussing the performance of this motor last fall.