Optimax failure analysis...

[Basshead35]

2007 Mercury Optimax 250 Pro XS Serial #: 1B492182

Question for Don or anyone who wants to take a shot.

Optimax powerhead failure piston Number two. All other pistons and bearings are fine.

New:
Water Pump
Fuel Pumps
Oil Pump
Air Injectors
Fuel Rail
Fuel injectors cleaned by European Marine
service items up to date.

Had a cracked front crankcase cover and replaced with a used compatible unit (2007 200 pro xs block front cover)
it developed a leak at the top crank bearing outer seal. I believe this introduced air in the system and possible burnt this piston. Lean mixture.

trying to get some feed back on possible cause. Below are attached pictures...

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[greg88]

I would agree on the lean part wow but not quite knowledgeable to trouble shoot from pics and current info.

[lpugh]

I tend to think overheated, better pictures including the cylinder walls, head crank and bearing would help. Possibly ring locating pin came loose allowing the ring to hang in a port which could rapid overheating of that cylinder due to reduced clearances. Is the locator pin still present in the ring groove and is the ring butted against it?
The white areas on the piston tops bother me a somewhat, but I am not an expert on these motors either

Though after that I would suspect you may have a bad direct injector from the contaminants introduced, have the complete fuel rails serviced to be safe

[Savage]

What damage occurred during the first repair, when the front half was replaced?

[Basshead35]

I don’t believe there was any damage from prior hairline crack. Replaced the front case half and ran several times with no power loss or any signs of damage. I recognized oil under the flywheel. Then proceeded to fix the oil leak. Once I repaired the seal I took it out and boom at 76 mph... no leaks after repair.

[JOE54]

first lets look at oil delivery to that cyl and has that cyl ever been repaired and where /which cyl was crack located, did #1 look lean ,closest to upper seal hmmmmm

[Savage]

I wonder if there was an installation problem with the seal restricting oil flow.

[Basshead35]

first lets look at oil delivery to that cyl and has that cyl ever been repaired and where /which cyl was crack located, did #1 look lean ,closest to upper seal hmmmmm

Oil deliver is good. New oil pump and did oil pump prime with Diacom software. l lost a piston ring locator pin on my last outboard (Ficht Evinrude) and the pin smash into the top of the piston about 50 times small indentions and broke a ring. This situation the piston melted. I do not believe a pin came loose.

There were two cracks that ran underneath the fwd lower part of the intake and the other on the port side around mid way up. First one was about 4” and the port side was 3”. Only leaked at wot. Possibly had an affect but The engine ran great after repair. Took out several times. Then discovered the leak at top bearing.

below are pics of the starboard side pistons after the #2 blew. And the starboard cylinder head. Does not appear to be lean. The plugs are new. Run Don’s cocktail every tank.

where can i get gasoline near me

[FastCat04]

Just my thoughts...and possibly totally wrong....but here goes:
You top crank seal air leak would have only affected cylinder #1 (top starboard side). You lost #2. Which could have been from lean, overheat, or lubrication.
1) lean---air leak or blocked injector
2) overheat---thermostat(unlikely) or blown gasket at exhaust tuner/mid-section connection..which would then fill the incoming water passage way with exhaust (bubbles) which would rise to top and disrupt cooling up there
3) lubrication---injector may have stuck open and flooded cylinder with fuel continuously thus washing the cylinder walls of lubrication and galling the piston. Look into the exhaust port on cyl #2 and compare it to the others. If it's clean...this is probably the root cause.

5 pics below are of a 2015 250 ProXS PH I purchased just for my personal education & understanding (not original poster's engine)

[Basshead35]

Just my thoughts...and possibly totally wrong....but here goes:
You top crank seal air leak would have only effected cylinder #1 (top starboard side). You lost #2. Which could have been from lean, overheat, or lubrication.
1) lean---air leak or blocked injector
2) overheat---thermostat(unlikely) or blown gasket at exhaust tuner/mid-section connection..which would then fill the incoming water passage way with exhaust (bubbles) which would rise to top and disrupt cooling up there
3) lubrication---injector may have stuck open and flooded cylinder with fuel continuously thus washing the cylinder walls of lubrication and galling the piston. Look into the exhaust port on cyl #2 and compare it to the others. If it's clean...this is probably the root cause.

Very interesting points. I will look at this when I get home. Thanks!!

[EuropeanAM]

Fastcat... try to avoid posting pictures into someone's thread like that, it proves to be very confusing when trying to review the entire thread. Thanks!

Basshead35... from the looks of the CROWN of the piston in #2, I do not believe that cylinder was lean. Especially considering you can still easily distinguish the carbon and burn pattern (despite the pulverized aluminum).

If that's the rod bearing for #2, I doubt it is an oil delivery problem either.

What do you have in the Run History and Freeze Frame (Fault) History?

There's little doubt that the upper ring hung in a port, it literally ripped the crown off the piston and spiral-shaped the ring. The usually occurs with debris in the port, locating pin failed, or cold seizure. Inspect/test the thermostat on that bank (also).

[Basshead35]

Fastcat... try to avoid posting pictures into someone's thread like that, it proves to be very confusing when trying to review the entire thread. Thanks!

Basshead35... from the looks of the CROWN of the piston in #2, I do not believe that cylinder was lean. Especially considering you can still easily distinguish the carbon and burn pattern (despite the pulverized aluminum).

If that's the rod bearing for #2, I doubt it is an oil delivery problem either.

What do you have in the Run History and Freeze Frame (Fault) History?

There's little doubt that the upper ring hung in a port, it literally ripped the crown off the piston and spiral-shaped the ring. The usually occurs with debris in the port, locating pin failed, or cold seizure. Inspect/test the thermostat on that bank (also).

The bearings on #2 are fine. All bearings look like the picture. I have it completely torn down and am unable to pull freeze frame at the moment. I do know I always let it warm to 120 and above before launch.

There was a strange cooling issue. I did have an issue with the starboard (not the port) thermostat which I replaced.

I know the merc monitor is an average of the two temp sensors, so unless I have the computer pulled up I do not know what each individual bank is cooling at, but at idle the temp would hover in one spot and not always cycle. It would cycle on startup and after a run when I come off plane but if I idled for a period of time or on the ears it would hover and stay around the same temp. Mostly 120-122...

[lpugh]

I agree with Don on this and I might add the fueling will be the same even with a air leak unless it is great enough that you would run less throttle reducing TPS signal, I can not even imagine that happening though.

[EuropeanAM]

BTW... hope that index finger is healing. Ouch!

[Basshead35]

BTW... hope that index finger is healing. Ouch!

Haha it’s an illusion and I believe it’s the master gasket (red) Looks like blood...

[greauxpete]

Aren't the crankcase covers lined bored for individual blocks?
Could this be a culprit?

[EuropeanAM]

Technically, yes, but I doubt that this is the cause (there would be crankcase area damage).

Of course- make sure there is nothing "missing" from the #2 reed block, and as much as possible, inspect piston for locator pins (if pins are gone, for evidence of ring rotating).

Also check exhaust port for grooves indicating ring hung in the exhaust port (I suspect you will find evidence of this).

[Basshead35]

Technically, yes, but I doubt that this is the cause (there would be crankcase area damage).

Of course- make sure there is nothing "missing" from the #2 reed block, and as much as possible, inspect piston for locator pins (if pins are gone, for evidence of ring rotating).

Also check exhaust port for grooves indicating ring hung in the exhaust port (I suspect you will find evidence of this).

Ok I will inspect for this. Reeds are intact and no missing pieces including #2 (New Carbon Fiber Reeds from European Marine compliments of Don) The pin location is so damaged it is pretty much impossible to see. I will see if the ring rotated... Is pin failure a common occurrence?

I sent my last engine Evinrude pistons to a guy in California (John Marles US1 Racing) who relocated the pins to prevent this from happening. That engine had a pin failure. Other than relocating pin, is there a way to prevent pin failure??

Thank you for the advice and direction.

Two questions:
Will the 2007 200 Optimax Pro XS block work for the current 250 pro XS engine. If so it may be more cost effective to use the spare block that I have.

The exhaust port of the #2 of the current block broke a chunk of the sleeve out and will need to be re-sleeved.

If the 200 block will work. Is there an identification number on the block for me to verify that it is indeed a pro xs 200 block part number?

I will talk to machine shop and see which repair route is most effective...

Thank you!!

[EuropeanAM]

Locator pin failure isn't real common on the 3L product (assuming it's being run within the recommended RPM's, not being overheated, and not constantly hammering the limiter).

200 block is NOT suitable. Completely different exhaust porting (200/225/250 each have a different port profile). Resleeve the 250 block for best results.

Just a suggestion: I would NOT re-use the rod from #2 under any circumstances. It's been through some pretty rough "strokes".

[Basshead35]

I figured the rod would be bent. Will do thanks for the advice. Also I did have a 27 Fury I ran and could never get it in the right RPM range which has been working on my mind as a possible issue. I switched to a 26 pitch trophy and not long after I switched (2 outings), it blew. 27 could have been a factor. Regardless this will all be resolved prior to completion of repair...