Melted piston

[Greggw/2g's]

I have a 2005 Merc. 2.5 Optimax xs, 225hp, on a 20' Hydrostream. The motor has 150 hours on it. The # 5 piston melted in the cyl. and disconnected from the connecting rod.
My question is what would have caused this. I use Merc. oil, and 92 octane fuel?
I dident thing this could happen to such a computrized motor. I would think the computer would have sent an alarm and or shut the motor down before melt down?
Any thoughts or input?

[RNM018]

As good as these newer motors are , they can still have there moments . Sounds like it leaned out for one reason or another . When there turning in there upper rpm range ,it can be hard to notice a slight loss of power . So , if you don't reconise what's happening ,this is how it ends .

Remember , the piston/cylinder started to feeling bad . He still had 5 freinds tring to drag him out to the party !

Sorry For Your Misfortune !

Rich Martin 018

[Greggw/2g's]

Thanks,

[AwesomeBullet]

There is nothing the computer can do to monitor injector flow or mechanical defects in the engine....trust me, I know lol!

[Evolution Marine]

sorry for your loss thats a great engine but over 5 years with only 150hrs id say it was fuel problem. #5 is 1st to go when lean out. jmo Todd

[HStream1]

Like Rich said something caused that "cylinder to lean out" causing a temp spike. Just currious what do the other five cylinders look like?

[albypine]

[QUOTE=RNM018;1901243]As good as these newer motors are , they can still have there moments . Sounds like it leaned out for one reason or another . When there turning in there upper rpm range ,it can be hard to notice a slight loss of power . So , if you don't reconise what's happening ,this is how it ends .

Remember , the piston/cylinder started to feeling bad . He still had 5 freinds tring to drag him out to the party !

Sorry For Your Misfortune !
rich are you one of those friends that drags the hurt friend out untill he is stuck to a wall or floor party on, youll be all rite,

[slowaction420]

water in the gas ,junk in the vst ,bad fuel or air injector ,loss of low psi fuel pump
any of the above and BANG its all over

[Capt.Insane-o]

It does'nt have to be lean, I've seen many that the fuel injectors flood on. They soot up the top of the piston with carbon. Then you have what they call "an uncontrolled combustion event".

[wideglide55]

I'd rebuild it and sell out for a staight EFI.

[Capt.Insane-o]

With the fuel situation these days letting any motor sit for an extended time without use is not good. Constant use of fuel stabilizers is an absolute must along with regular injector service.

[Greggw/2g's]

Thanks for all the input. The other cylinders look fine. Only # 5 has a hole right in the center of it.
I hope to get the piston out and check the block (keeping my fingers crossed). I was told it could be resleeved if thats the only damage (knowing my luck thats not the case)
How hard is it going to be to get parts for this engine being its "Mercury Racing" and how much more $$$ then stock? Worst case a new power head?

[wideglide55]

I never ran any gas over 2-3 weeks old,stabilized or not,would pump it out and run it in my truck.

[Capt.Insane-o]

Thanks for all the input. The other cylinders look fine. Only # 5 has a hole right in the center of it.
I hope to get the piston out and check the block (keeping my fingers crossed). I was told it could be resleeved if thats the only damage (knowing my luck thats not the case)
How hard is it going to be to get parts for this engine being its "Mercury Racing" and how much more $$$ then stock? Worst case a new power head?

They are not a hard engine to rebuild, just time consuming. There are aftermarket, oversized pistons on the market as sleeves as well. The real cost comes in the servicing of the injectors, pcm and compressor to find out WHY it stuck. The air injectors are near 400 dollars a piece, and the fuel around 180 if any need replacing.

[Dave S]

All the save gas motors cost in the end. I think I will have a nudda.