2006 225 ProXS broken piston

[bassinvol]

IMG_7073.jpeg IMG_7075.jpeg
2006 225 ProXS 940 hrs
SN 1B371949

I was running across Guntersville the other day and things went from good to bad. It looks like a section from the number 5 piston ring land broke off and went down the exhaust port. No damage to the head at all. I am planning on rebuilding the entire motor. I was looking for oversized Mercury pistons but can’t seem to find anything but standard or aftermarket pistons. Are oversized Mercury pistons available, or will I have to go with aftermarket pistons? If so, what brand do you recommend?

[lpugh]

#5, meaning bottom starboard side?

[lpugh]

#5, meaning bottom starboard side?
Looks lean, have all the injector validated.
INTEGRITY Injection (by European Marine) offers Injector Service and Calibration!

[lpugh]

#5, meaning bottom starboard side?
Looks lean, have all the injector validated.
or loss of lube to that cylinder

[bassinvol]

That is correct.
The dry part probably comes from the 6 1/2 mile idle that I did to get back to the ramp. I knew it was idling rough, but it was running.

[lpugh]

That is correct.
The dry part probably comes from the 6 1/2 mile idle that I did to get back to the ramp. I knew it was idling rough, but it was running.

Nope, just the opposite would occur.

[bassinvol]

Nope, just the opposite would occur.

I’ll just have to disagree. With no compression, there is also no vacuum to pull intake air/oil into the cylinder through the intake port. With gas still being pushed into the cylinder, ignition and poor combustion would wash the piston. At least that’s the way I see it.

[lpugh]

No vacuum or air flow=no run my friend
Though you may see it on a vacuum gauge, there is still a vacuum and air flow thru the crankcase which does in fact move some oil. Due to closed throttle and very low cylinder pressure the motor will have incomplete combustion, carbon buildup and may foul spark plug, The one big disadvantage of two stroke motors.
have you not seen a set of plugs that came of one of these motors with extended low rpm use?
Incomplete combustion is different than fuel wash from no combustion.
Yours shows a very lean or lack lube problem, hot and dry and no black carbon at all
Possible overheat, butt other cylinders would be affected as well.

[bassinvol]

IMG_7070.jpeg

Plenty of carbon buildup on the plug. You do realize that each cylinder intake is separated behind the reed plate from each other?
But back to the main question, are Mercury oversized pistons available.

[lpugh]

I know these motors very well. 50 years of experiance

[ChrisCarsonMarine]

I don't believe factory oversize are available,but we have great aftermarklet ,Chris

[JOE54]

^^^^^^ yep std only

[EuropeanAM]

I would expect that DI to be trashed... and as is most commonly the case, this was a ring that hung in the exhaust port, which halted the piston until the crown was ripped off (the crack in the piston may have occurred earlier OR later).

Looking at the dish in that piston... it probably was NOT a lean condition. The condition of the connecting rod and wrist-pin bearings will help to tell more of the tale.

Sleeve it back to STD size, or use aftermarket/oversize. Not really big on aftermarket stuff, but the WSM oversize pistons seem to hold up pretty well from what I've seen.