piston damage 18ME2 tohatsu 2 stroke

[grouper242]

Hello, hope I can get some info and help with this.

[robert graham]

Sounds like a piston ring got snagged in port, breaking the ring, chipping piston, grooving cylinder wall. The ring may have been stuck in it's groove with carbon build-up....how old is the motor? Yamaha sells a product to add to fuel called Ringfree to prevent this....

[TownsendsFJR1300]

Why did it seize up the last time, any obvious clues (short of the internal damage)? Was the engine run on pre-mix oil/fuel?

To get it running again would involve boring the block to the next, larger adequate size plus a new piston and rings.

Depending on how much larger you go on the bore, it may be best to bore both cylinders..

[robert graham]

I'd bet the first seize up was just rusted rings/cylinder walls....

[TownsendsFJR1300]

I'd bet the first seize up was just rusted rings/cylinder walls....

+100 ^^^.

And for the OP, WHERE on the piston is it chipped, by the rings?

There is a small "pin" that is supposed to keep the rings from rotating around the piston and getting stuck in a port.

Did you happen to notice if that pin is still there and is there damage to the rings?

I suspect $ wise for machine work and new parts, it'd be cost prohibitive to repair..

Can you post some pic's?

[rodbolt17]

do you understand why it seized when it got hot from neglect?

it was because the pistons swelled and got larger than the bore diameter.
it typically wastes a piston.

may take another few hours to fail but fail it will.

overheat due to lack of maint killed more two strokes than malboros killed cowboys.

oh, it will kill fourstrokes almost as fast.

I cant tell you how many motors I have seen folks let sit 4+ yrs and expect them to run without cleaning the fuel system and fixing the cooling system BEFORE running them.

kept my machinist and I busy for a long time.

[rodbolt17]

dude
that impeller is rubber.
it fails with time OR use.
time will cause instant failures.
may take a few hours to shred a 5 yr old impeller but when it shreds the results are catastrophic.

bites but that is how it works.

cant tell you how many otherwise fine running engines have been destroyed cause the water pump,at 10 yrs old, worked when we left the dock.

it is called maintenance for a reason.

see if it is boreable, check for excessive corrosion in the cooling passages, if the rod,main and wristpin and pin bearings are ok reuse them.
I never reuse the bottom ball bearing.