A new MerCruiser rocker/oil problem, and a related question:

Jodijoe

My port 496 Mag quit on me the Friday before Labor Day weekend last summer. The season was winding down so I used it as a floating condo for the last 6 weeks of the season to avoid paying another $1100 of in and out lift fees to have it repaired quickly enough to catch the last month of the season. The marina was supposed to fix it over the winter but they didn't get around to it until a month ago or so. I thought maybe the issue was related to the fuel rails and injectors not being repaired properly (see my other thread), but it turns out the rockers cracked due to poor quality design or construction. It took the shop a long time to determine the problem. I formally asked MerCruiser to send out a rep to determine the problem but they failed to send a rep. My service manager finally fixed the problem himself. When he was testing the engines, a rocker on the starboard engine failed. Both engines down, he had racing grade rockers made. The problem is that he only replaced 4 of the 32 rockers. He asked if I run the boat at WOT for long periods of time and I said only to get up on plane. Could the performance be related to the painted fuel rails/injectors issue? I'm now afraid to attempt to get up on plane for fear that another rocker will blow early in the season and be relegated to miss more boating season to get in a long service line again so soon. Engines should be able to handle getting up on plane without rockers breaking apart. Check out these photos:

Jodijoe

Black_Diamond

You have a lubrication issue most likely or they were installed improperly.  For those rockers to turn blue like that they were in excess of 600F. 

I would have pulled the others and looked for wear/heat affected zones. Is this a stock/OEM engine?

LaRea

By replacing the OEM rockers with "racing grade" rockers, your mechanic slapped a bandaid on a potentially serious problem.  Maybe the new rockers will last, but if the root problem still exists, the new rockers will probably fail just like the OEMs did.  So, yes - you should be afraid to get up on plane. 

Black_Diamond

This might be worth checking depending on your engine year and S/N:

MERCRUISER SERVICE BULLETIN 2001-6 "Required 496 MAG **** / 8.1S 
**** Push Rod Replacement" 
2001-2002 MCM 496 MAG **** sterndrive engines (s/nos OM025976 
through OM025985 & s/nos OM061091 through OM061773) and MIE 
8.1S **** inboard engines (s/nos OM026663 through OM027049) 
Warranty codes: MM72, MX16 & Uniform Failure Observation (UFO) 423 
-40 

Jodijoe

Black_Diamond said:

You have a lubrication issue most likely or they were installed improperly.  For those rockers to turn blue like that they were in excess of 600F. 

I would have pulled the others and looked for wear/heat affected zones. Is this a stock/OEM engine?

OEM engine. I'm the one who had the fuel rails and injectors changed due to the paint chips. I know nothing about engines, so sorry for my ignorance, but could the rocker have overheated due to the fuel rails/injectors repair work? Did they forget to add more oil? What would cause that high heat?

Jodijoe

LaRea said:

By replacing the OEM rockers with "racing grade" rockers, your mechanic slapped a bandaid on a potentially serious problem.  Maybe the new rockers will last, but if the root problem still exists, the new rockers will probably fail just like the OEMs did.  So, yes - you should be afraid to get up on plane.

THank you. Can you offer a short list of possible root causes of the problem? Do you think there was damage from the fuel rail/injectors? What actions should I take next?

zaverin1

No.
fuel rail and rockets are completely different systems 

Jodijoe

Black_Diamond said:

This might be worth checking depending on your engine year and S/N:

MERCRUISER SERVICE BULLETIN 2001-6 "Required 496 MAG **** / 8.1S 
**** Push Rod Replacement" 
2001-2002 MCM 496 MAG **** sterndrive engines (s/nos OM025976 
through OM025985 & s/nos OM061091 through OM061773) and MIE 
8.1S **** inboard engines (s/nos OM026663 through OM027049) 
Warranty codes: MM72, MX16 & Uniform Failure Observation (UFO) 423 
-40 

Thank you. No luck with the serial numbers. Any other thoughts?

69fastback

That is not a rocker issue. Chevy has been using those same rockers for many years and I've never seen one do that. You've got an oiling issue of some kind. 

Black_Diamond

The heat/blueing is from friction without lubrication.

 Were the failed rocker arms on the exhaust valves only? 

you might ping 212rowboat too. Super knowledgable engine guy on here. 

Cableguy Greg

Jodijoe said:

Black_Diamond said:

This might be worth checking depending on your engine year and S/N:

MERCRUISER SERVICE BULLETIN 2001-6 "Required 496 MAG **** / 8.1S 
**** Push Rod Replacement" 
2001-2002 MCM 496 MAG **** sterndrive engines (s/nos OM025976 
through OM025985 & s/nos OM061091 through OM061773) and MIE 
8.1S **** inboard engines (s/nos OM026663 through OM027049) 
Warranty codes: MM72, MX16 & Uniform Failure Observation (UFO) 423 
-40 

Thank you. No luck with the serial numbers. Any other thoughts?

Keep in mind the O at the beginning is the number zero (0) not the letter O.

LaRea

Truth is, you might never find the root cause.  If a PO ever ran the engines hard with low oil or cooling water, it could cause any number of latent problems that would be hard to diagnose.  An engine scan will tell you the number of hours spent at wide open throttle (WOT), and that could be an indicator.  

Honestly, broken rockers are rare in Merc engines (really, all GM engines).  As far as I know, it only happens under unusual circumstances. 

Out of curiosity, did you purchase a professional engine survey before buying the boat?

Jodijoe

LaRea said:

Truth is, you might never find the root cause.  If a PO ever ran the engines hard with low oil or cooling water, it could cause any number of latent problems that would be hard to diagnose.  An engine scan will tell you the number of hours spent at wide open throttle (WOT), and that could be an indicator.  

Honestly, broken rockers are rare in Merc engines (really, all GM engines).  As far as I know, it only happens under unusual circumstances. 

Out of curiosity, did you purchase a professional engine survey before buying the boat?

One of the regular service techs worked on it for awhile and couldn't find the problem. My service manager who did the repair said he has never seen rockers break either. I paid a reputable surveyor. I assume he surveyed the engines, too. We did the sea trial at WOT for a few minutes. I seem to remember something about an oil test. Is that what you mean? Or is there another entire survey category just for the engines? I asked the service manager what was the Vessel View code and he fumbled through the answer so I'm still not sure. It looks like we're going to have a summer of displacement hull boating.

rasbury

I had a survey done but that was mainly Hull and test the systems- no in depth engine check out.

LaRea

A separate engine survey is more common on larger yachts, but a combined survey is common for boats like ours.  The oil test might tell you something, so definitely get a copy of that.  Some of the smartfolk here on the forum can help interpret it if you're willing to share details.  

Ian

Jodijoe said:

Black_Diamond said:

This might be worth checking depending on your engine year and S/N:

MERCRUISER SERVICE BULLETIN 2001-6 "Required 496 MAG **** / 8.1S 
**** Push Rod Replacement" 
2001-2002 MCM 496 MAG **** sterndrive engines (s/nos OM025976 
through OM025985 & s/nos OM061091 through OM061773) and MIE 
8.1S **** inboard engines (s/nos OM026663 through OM027049) 
Warranty codes: MM72, MX16 & Uniform Failure Observation (UFO) 423 
-40 

Thank you. No luck with the serial numbers. Any other thoughts?

His “poor Mercrusier thread” states. 2008 engine so this seems before.

Jodijoe

Black_Diamond said:

The heat/blueing is from friction without lubrication.

 Were the failed rocker arms on the exhaust valves only? 

you might ping 212rowboat too. Super knowledgable engine guy on here. 

Yes, both rockers were on the exhaust end. My service manager said the push rods should have bent first before these would have cracked. He recommends getting all the rockers changed if this happens again. 

69fastback

Jodijoe said:

Black_Diamond said:

The heat/blueing is from friction without lubrication.

 Were the failed rocker arms on the exhaust valves only? 

you might ping 212rowboat too. Super knowledgable engine guy on here. 

Yes, both rockers were on the exhaust end. My service manager said the push rods should have bent first before these would have cracked. He recommends getting all the rockers changed if this happens again. 

I think putting new rocker on is just throwing parts at it hoping it goes away. There's another underlying issue. 

rasbury

The rockers are just like the last chain in the link right? I have never heard of these frying out like this- unless they were just bad parts but so unlikely....I dunno....

Black_Diamond

Exhaust side makes sense being the warmer valve. Bad parts would honestly be rare. 

rasbury

How could you have that kind of rocker damage (heat) and not damage either push rods or valves/pistons and rings? Compression check in order? Running super lean??

randy56

I've heard of oil pump's get weak, go bad, or clogged with part's of derbies from oil filter, and or cheep crappy oil, or oil additives. Not in Mercruser, but auto engines. Oil is a coolant, does not look like enough is getting up there. The problem is not solved.  I'm surprised the temperature gauge was not pegged, while underway. 
if it was mine I would start it with valve covers off. To see oil flow.

212rowboat

what cooling system is on these engines? 
i may have missed it, but what cylinders were these atop?

the very first thing is where they broke.  they appear ripped right off the pedestal.  they ain't supposed to move except over the ball cap... any up and down from improperly torqued rockers or from a stud pulling even slightly and you have forces changing from focused on the ball to on the stud- where no oil system can assist... it's often confused with deflection, but it's not.  it's basically testing the meddle of a bolt/stud's sheer strength as opposed to it's torsion strength and for which it was designed...

imagine it being held snug- such as a wheel is held snug to the hub.. it can take all kinds of weight and abuse so long as it doesn't wiggle.. if it can wiggle? you've not only created a new friction point outside the design envelope, but each time the wheel shifts it gets a running start without resistance until it slams onto stud.... same principle here.. if that rocker was loose even a little bit it would soon be a lot as the stud further pulls from the head and/or stretches... it wouldn't do that without a head start....  

if it were hydro lock the push rod would most likely have bowed first, or snapped.  i'd be curious to see those.  if the valve springs were floating *basically the springs compressing to the point they can't rebound quick enough to close completely there could have been some wiggle created- but what those pictures indicate isn't something that happened like that with the discoloring- it was done over time.  besides, they'd have to been REALLY loaded for extended periods for that to be a concern.  

i'm going to go with bad install (improperly torqued) rockers OR a stud pulling (but twice?) as a secondary. i'd like to see a pic of the pushrods under those two, though, as a bend could indicate a leakage in the cooling system under load and RPM that caught it just right. 

do you allow the engines to reach full operating temperature before slamming WOT? thermal expansion and married surfaces tasking gaskets (especially cold water from a raw system) could cause a momentary leak on a soon-to-be-failing cooling system and cause the carnage... which will again be evidenced by bent push rods.  

Jodijoe

rasbury said:

How could you have that kind of rocker damage (heat) and not damage either push rods or valves/pistons and rings? Compression check in order? Running super lean??

The service manager said it was running rich, but my fellow dock mate who completed the Mercruiser mechanic courses decades ago said it sounded more like it was running lean. Could the problem be related to improper fix of the fuel rails/injectors recall repair? 

Jodijoe

212rowboat said:

what cooling system is on these engines? 
i may have missed it, but what cylinders were these atop?

the very first thing is where they broke.  they appear ripped right off the pedestal.  they ain't supposed to move except over the ball cap... any up and down from improperly torqued rockers or from a stud pulling even slightly and you have forces changing from focused on the ball to on the stud- where no oil system can assist... it's often confused with deflection, but it's not.  it's basically testing the meddle of a bolt/stud's sheer strength as opposed to it's torsion strength and for which it was designed...

imagine it being held snug- such as a wheel is held snug to the hub.. it can take all kinds of weight and abuse so long as it doesn't wiggle.. if it can wiggle? you've not only created a new friction point outside the design envelope, but each time the wheel shifts it gets a running start without resistance until it slams onto stud.... same principle here.. if that rocker was loose even a little bit it would soon be a lot as the stud further pulls from the head and/or stretches... it wouldn't do that without a head start....  

if it were hydro lock the push rod would most likely have bowed first, or snapped.  i'd be curious to see those.  if the valve springs were floating *basically the springs compressing to the point they can't rebound quick enough to close completely there could have been some wiggle created- but what those pictures indicate isn't something that happened like that with the discoloring- it was done over time.  besides, they'd have to been REALLY loaded for extended periods for that to be a concern.  

i'm going to go with bad install (improperly torqued) rockers OR a stud pulling (but twice?) as a secondary. i'd like to see a pic of the pushrods under those two, though, as a bend could indicate a leakage in the cooling system under load and RPM that caught it just right. 

do you allow the engines to reach full operating temperature before slamming WOT? thermal expansion and married surfaces tasking gaskets (especially cold water from a raw system) could cause a momentary leak on a soon-to-be-failing cooling system and cause the carnage... which will again be evidenced by bent push rods.  

THANK YOU SOO MUCH.

UPDATE: The split rockers were from Starboard #8 and Port #6, both exhaust side. My service manager installed 4 racing rockers and advised all the rockers be changed if this happened again. My boat was cleared on May 10. I ran it at around 1200 rpms because we had a boating event to attend this past weekend and I was afraid it would fail. Sure enough, yesterday, May 19, coming back from the event, I pushed it up to 1500 rpms near my marina, rpms were different from each engine. Port engine stalled and wouldn't restart. Had to pull in on one engine. Repair lasted one week. Same symptoms as Labor Day weekend last summer. Sounds like more rocker problems? Stern drives. Not sure which cooling system. Could this have been the result of screwing on the rockers too loosely? Would the rockers have been loosened or removed during the recall repair of the fuel rails and 16 injectors? I'm just trying to understand so I can keep my boating sanity.

THANK YOU SOO MUCH.

Jodijoe

Adding to the above post: I don't run WOT on cold engines. Not sure about the previous owners, but the boat ran at WOT during my sea trial and no failures there. No bent push rods per the service manager.

Cableguy Greg

I was talking with the mechanic at my marina and he though that they were over torqued. From what he says, they are supposed to be tightened down, then backed of X ft/lbs per rocker. I should have looked at your engines this past weekend. I would have been able to tell you if they were Horizon engines. I don't think that they are, but it has been 9 years or more since I have been in the engine room on your boat. I just remember it has Axius.

zaverin1

1500rpm and it failed?
and
no internals stay put during fuel rail repair

Jodijoe

Cableguy Greg said:

I was talking with the mechanic at my marina and he though that they were over torqued. From what he says, they are supposed to be tightened down, then backed of X ft/lbs per rocker. I should have looked at your engines this past weekend. I would have been able to tell you if they were Horizon engines. I don't think that they are, but it has been 9 years or more since I have been in the engine room on your boat. I just remember it has Axius.

The engine did not overheat any of these times. The port engine just silently quit both times. I believe it was while decelerating because both times I was approaching the marina no wake zone and eased off the throttle, even if only doing 1500 rpms yesterday, if that history helps.

So is it likely to be a manufacturing defect if the rockers were overtorqued when the engine was constructed?

It sounds like 212rowboat thinks the rockers were under torqued, loose, and the repetitive wiggling under pressure split them apart.  What other repair would necessitate a mechanic loosening the rockers? The boat has <200 hours. Although, they do appear to be bluish or maybe heated. 

zaverin1

You need engine tear down