Merc 90hp -89 broken piston

My old Merc went broken last week after a few distinct bangbangbang.

Took the motor and powerhead apart and found that one piston was broken above the upper piston ring on approx one third of the perifiri of the piston top. Loose parts from piston blocked the engine from rotate. No marks on cylinder walls but...

...it looks like the cylinder lining has moved somewhat. Specifically on the cylinder with the broken piston but also, but less, on the other cylinders.

(Could this be the root cause for the piston to break)

If, but only if, the cylinder lining is expected to be positioned tight to the cylindertop, the worst cylinder lining is off some 3mm .

Is this a known issue with these Mercs ?

Can the cylinder lining be pressed back and expected to stay there for "another 20 years" or is it destroyed because it ones have moved out of position ( if it has)?

If possible how to do it? Just press or use some cold / heat treatment. Was thinking of heating the powerhead in th owen to 100 deg C and then insert a deep froozen piston into the cylinder and hope for the lining to be colder and crimp before pressing it back.

Re: Merc 90hp -89 broken piston

If the liner has rotated then the piston rings can and will snag in the ports causing extensive piston damage.

The liners shift is often caused by a couple of factors, one, engine temp, two piston rod straightness.

Re-aligning used liners is risky, the fit of the liner to the block may be lessened by the movement and it is possible for the liner to shift again. It is recommended to replace the liners with new liners which are slightly oversize outside dia. for a proper interference fit.

Check your rods very carefully for straightness, even the slightest 'twist' in the rod impart off-center thrust from the piston to the cylinder wall, contributing to liner shift.

Re: Merc 90hp -89 broken piston

On most of the inlines the liners are cast in place. I have never seen one live very long after the liner has moved. The merc book says you can't replace the liners. I would think you would loose the press fit if it moved any. I don't even bore mercs because most are blind bores and my machine does not do blinds.
I have a friend that does bore them on a mill. I'll ask him for any advice he could shed for you. Ok here's what he told me piston rod would be most likely the cause. Mark tells me if he finds a liner loose in boring at that point he makes a phone call. The liner can be press back in if it has not turned in the hole but he said you would never warranty any work from that point.

sorry I was no help here.