Hole in the top of 200 OX66 Piston

[jimmytanner]

--------------------------------------------------------------------------------
I have a buddy with a 2002 200 OX66. Last year he somehow got water into the engine and.......well you know.

Had the power head replaced and got the boat back in late October 2013. This year he has put about 15 hours on it doing the break-in. He said he noticed a slight knock (very Slight) in the engine and told the mechanic about this and he said just keep running it.

Of course, He last trip July 4th, It quits. tells me about it and we do a compression test. Well the # 6 Cylinder (bottom on port side) has a hole in the top. not burnt From what I remember, the plug was black and had Aluminum (filing looking pieces) the plug had no damage. ie bent electrode.

The shop gave him a one year warranty. He took it in around the 14th of July. they said No Problem we'll get it fixed and back to you soon. We have to check several things prior to filing a warranty claim.

He's very patient and we fish on my boat anyway.

Sept 26th he gets a call from the shop and they tell him that the engine company will not warranty the engine failure due to bad gas.

What are your thoughts?

[boscoe99]

Warranty normally covers defects in a motor due to materials or workmanship issues only.

Detonation damage (which I am assuming is the case with your friends motor) is externally induced damage. That is, the materials and/or workmanship were not defective. Something external to the motor caused the piston to become damaged. Could very well be bad gasoline. Could be an injector leaning out the one cylinder.

Same thing with a perfectly good lower unit. If it strikes an underwater object it becomes damaged. Due to no fault within the gear case itself. Something external caused the damage.

No one, or thing, is particularly at fault. This falls into the category of shit happens. Sorry.

Take a look at the link in this page to the article titled "how to destroy your engine..."

https://www.google.com/search?q=pist...ion+detonation

[Pete1681]

That stinks!Was the gas bad?Did he have a written warranty?Maybe get a second opinion,definitely would challenge,doesn't sound right,small claims court?

Good luck!

[rodbolt17]

about the only thing that will burn a hole in a piston is detonation.
causes for detonation are poor quality fuel,lean A/F mix in the cyl,to much ign timing advance,to much compression for the fuel grade in use,or overpropping.
if he was still running the fuel from oct 2013 on july 4th 2014 then I would suspect fuel quality.
without a full model number I cant say much more about it.
the OX66 was made in 2.6L and 3.1L versions and used different ign controls.

biggest reasons we ever see for detonated/burned pistons are overpropping,low fuel rail pressure and clogged injector filters.

[jimmytanner]

thanks I'll try to find out more info. Going to pull some fuel next week.

Would a clogged injector filter not cause a rough run?

[rodbolt17]

not until fuel is restricted enough at the A/F ratio becomes lean.
remember, fuel flow requirements change from idle to WOT.
at 38 PSI that injector may flow enough fuel to make life happy at 3800 RPM but don't try for 4500 RPM.

at 32 PSI the engine will run mostly ok but borderline lean.
don't do it.
at 32 PSI and over 4500 RPM its a six way race to see which piston fails first.

[boscoe99]

That stinks!Was the gas bad?Did he have a written warranty?Maybe get a second opinion,definitely would challenge,doesn't sound right,small claims court?

Good luck!

To those in the know, it does sound right. Right as in correct.

I would surmise that once the heads get pulled they will find damage or distress to other pistons or parts of the motor. What are the chances of two, three or more pistons all having a warrantable defect at the same time? Highly unlikely. Extremely improbable.

Let's assume just the one piston is damaged with a hole in it. Did the aluminum in that one piston just decide to come apart in the center of the piston? That is text book detonation damage. It is not a defective piston.

Let's say they pull the connecting rod and find evidence of excessive wear on the rod journal bearings. Big and small ends. Did those bearings just happen to be defective at the same time the piston was defective? Probably not. Detonation damage can destroy bearings, bend connecting rods, and all sorts of other nasty stuff.

It is not due to any part being defective. It is what is called induced damage. Something else caused that damage to occur. Is this the fault of the engine builder? No. Is it the fault of the boat owner? Probably not. DOes it suck? Yes. Is it unfortunate? Yes.

Do a google search and look up detonation and its ugly nasty red haired step sister pre-ignition. Read what causes it and read what it looks like.

[boscoe99]

thanks I'll try to find out more info. Going to pull some fuel next week.

Would a clogged injector filter not cause a rough run?

Actually, a leaner running motor can run smoother than a motor that is running at the design air fuel ratio, whatever that may be.

Too rich and it runs ruff. A bit leaner and it might not be ruff. A bit more lean and it might run ruff.

But at high power settings it is difficult to detect the ruffness in some motors.

A lean fuel injector does not always cause detonation. At some point if it is too lean it will not be making the power it should and that cylinder will start to run cooler than the other cylinders. Think about an injector that is clogged completely. The cylinder is not firing. How hot/cool will that cylinder be compared to the others?

[bajakeith]

burning up a piston

besides using the wrong battery,,not keeping fresh thermys and flushing with saltaway on the muffs....the most over looked service item on a two stroke is a decarbon..don't know what yammy calls it...mercury calls it "motor tune" omc calls it "power tune" and such ...and no I am not talking about "ring free" that's prevention in the fuel.. a two stroke should be decarboned around each 100 hrs so that the rings can transfer heat off to the piston lands and stay cooler...when you have carbon build up behind the rings cant transfer the heat off to the piston and guess what happens...Id say 1 in 50 might have even heard of this service......and that's on a good day!! also fuel goes BAD very fast now days and what octane ?

[rodbolt17]

regular use of ring free or a similar additive helps with carbon. a yearly treatment with YIEC or similar product helps as well.
use on both two and four strokes.
yes not only do the rings have a sealing function they also have a heat transfer function.
on a new powerhead at 15 hrs I would not suspect carbon.

if the injector clogged or failed on the OX66 and you kept pushing it I would place my money on the mechanical symptom being a connecting rod that's no longer connected.

[boscoe99]

15 hours time in about a year? Maybe on the same rotten gasoline? Maybe a bit over propped?

The perfect storm for detonation.

[rodbolt17]

yep, perfect.
only thing worse is a blow boater.
I have one now that wants us to change the impeller in the water on his bracket,sold the motor new nine years ago and he says it quit pumping the other day. its never had a pump and may not get one now.

he also says it wont run right but he has added fuel stabilizer to the same 12 gallon tank for 3 years so that cant be the problem.

[boscoe99]

I don't have any first hand experience with blow boaters but a guy that did told me they would pull into his marina, buy maybe all of five gallons of diesel yet want 100 pounds or more of free ice, free water, free mooring for a bit of time, all because of their "purchase".

And by the way, will you take a look at my Yamaha while you are at it? It does not run right. Don't know why. It ran just fine the year before last when I last used it.

[Tucker]

not until fuel is restricted enough at the A/F ratio becomes lean.
remember, fuel flow requirements change from idle to WOT.
at 38 PSI that injector may flow enough fuel to make life happy at 3800 RPM but don't try for 4500 RPM.

at 32 PSI the engine will run mostly ok but borderline lean.
don't do it.
at 32 PSI and over 4500 RPM its a six way race to see which piston fails first.

I'm sorry, I'm not getting it. Why would only 1-injector be not getting correct PSI if that PSI is a consistent rail pressure. Faulty injector? How can you check for that before it leans out a cylinder?

[boscoe99]

I'm sorry, I'm not getting it. Why would only 1-injector be not getting correct PSI if that PSI is a consistent rail pressure. Faulty injector? How can you check for that before it leans out a cylinder?

The fuel rail pressure may be 38 psi on all injectors. The fuel pressure within one of the injectors may be less than that.

If an injector has a clogged filter basket then when the engine is running the pressure within the injector (after the clogged filter basket) could be less than the rail fuel pressure.

Less fuel pressure means less fuel flow. Less fuel flow with the same amount of air means a leaner fuel/air ratio. A leaner fuel/air ratio, together with some other adverse situations, might result in one cylinder being damaged.

I suspect that what Rodbolt was talking about was all injectors maybe having a lower than normal fuel pressure. In which case all cylinders would burn leaner than normal. With then maybe just one of those leaner than normal cylinders causing a problem because of the other adverse issues.

Motor might run just fine in a lean condition at low power settings. Might not run so well at high power settings.