Go Back   Maxum Boat Owners Club - Forum > Maxum General > Engines
Click Here to Login

Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-20-2018, 06:32 AM   #1
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Post Mercruiser 3L push rod bent, rocker arm off center, clanking noise from engine

2007 Maxum 1800 MX, Mercruiser Alpha 1 Gen 2 engine. Smooth sailing until I've heard a very loud clanking noise. Towed the boat back, took the rocker cover off and found out that cylinder #3 rocker arms were off to the side sitting on cap rotators instead of valves (exhaust more than intake).

Took nuts off both rockers and found out that both push rods were bent. One rocker arm stud had a deep cut (exhaust side) and even the head had a notch grinded by the push rod! (see pictures).

Got the new parts (rods, rocker arms, stud) but I'm not sure about 2 things:
1) what could possibly cause those push rods to be bent?
2) how to replace the rocker arm stud

Could a faulty hydraulic valve lifter cause that? Perhaps the valves weren't adjusted properly? Has this happened to you? Any ideas?
I just bought this boat few months ago. The previous owner had the cracked head replaced a year ago.
Attached Thumbnails
RockerArmsOffCenter2.jpg   RockerArmsOffCenter.jpg   RockerArmStud.jpg   BentPushRods.jpg  
__________________

Maxum1800MX is offline   Reply With Quote
Old 05-20-2018, 11:42 AM   #2
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Hard to say why they bent but I would pull the head to check the valves as the stems could be bent as well. Maybe they went set right from the last repair, studs could be pulled out some as they are pressed in. Maybe water in that cylinder, since both valves this could be the cause. Pull the spark plug to look for water. I have not seen a collapsed lifter cause this but it may be possible.
__________________

__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-20-2018, 02:04 PM   #3
Commander
 
Gugi47's Avatar
 
Join Date: Apr 2018
Location: Afghanistan
Posts: 332
Send a message via ICQ to Gugi47 Send a message via AIM to Gugi47 Send a message via Yahoo to Gugi47 Send a message via Skype™ to Gugi47
Default

Hard to say but have to be inside the engine...Broken cam shaft? or damage piston?
If you don't know how engine should be fix, don't try to fix your self. You end up to pay more then you should.
Sorry for your problem considering the summer just start....
__________________
If they respect you, respect them. If they disrespect you, still respect them. Do not allow the action of others to decrease your good manner, because you represent yourself not others.
-2001 Maxum 2100 SR2 Sport -1997 Regal 258 Commodore (Sold)
Gugi47 is offline   Reply With Quote
Old 05-20-2018, 03:08 PM   #4
Commander
 
donald's Avatar
 
Join Date: Jun 2016
Location: N.Calif.
Posts: 415
Default

1+ for what Mike said.
Pull the plugs out and check for water.
If no water pull the head off you will probably find bent valves.
Don
__________________
1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
1976 16ft. Tahiti 2.5 IO (sold)
donald is offline   Reply With Quote
Old 05-20-2018, 04:57 PM   #5
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Default

Thanks for the tips. I'm trying to avoid taking the head off as this would be a major job. There seems to be no water in the engine, the oil is clean. I've installed new push rods, re-adjusted all rocker arms and started the engine. The engine runs fine, steady and quiet but because of that cut in the stud, one rocker arm slides right into it and shifts to the side almost immediately unless you hold it in the position manually by hand.

I'll take off the push rod cover next and check the hydraulic valve lifters.

No, I'm not a mechanic, I'm a software developer but I've got a good friend who is machinist to help me out plus I've got the service manual and the fellow boat owners to share the knowledge When I called the shop they told me $1000 just to diagnose the issue, so trying to save the dough and learn something in the process
Maxum1800MX is offline   Reply With Quote
Old 05-20-2018, 06:27 PM   #6
Commander
 
jrsick's Avatar
 
Join Date: Oct 2011
Location: Chesapeake, VA
Posts: 487
Default

I believe the loose stud is the cause of your problem.
Looks like the rocker stud loosened from its mount which created excessive lash. The rocker became a hammer and bent the pushrod.
The only way I know to fix that stud is to tap the stud hole and screw in a new one.
__________________
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine
jrsick is offline   Reply With Quote
Old 05-20-2018, 10:40 PM   #7
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Default

Hi jrsick, unfortunately the stud is not loose. I've put 2 nuts on it to try rotating it and nothing. It sits solid in the head.

The original studs have thread on one side only (16-34522). Is there a replacement stud with threads on both sides? Can't find any on their site other than original.
Maxum1800MX is offline   Reply With Quote
Old 05-20-2018, 10:58 PM   #8
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by jrsick View Post
I believe the loose stud is the cause of your problem.
Looks like the rocker stud loosened from its mount which created excessive lash. The rocker became a hammer and bent the pushrod.
The only way I know to fix that stud is to tap the stud hole and screw in a new one.
This would not explain both push rods bending.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-20-2018, 11:00 PM   #9
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by Maxum1800MX View Post
Hi jrsick, unfortunately the stud is not loose. I've put 2 nuts on it to try rotating it and nothing. It sits solid in the head.

The original studs have thread on one side only (16-34522). Is there a replacement stud with threads on both sides? Can't find any on their site other than original.
The OEM studs are pressed in and require sealant as they go into the coolant passage. If she is not making any tapping noise the lifters are not the issue.

There are screw in studs but the head should be removed as you will need to cut threads to install it.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-20-2018, 11:01 PM   #10
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by Maxum1800MX View Post
Thanks for the tips. I'm trying to avoid taking the head off as this would be a major job. There seems to be no water in the engine, the oil is clean. I've installed new push rods, re-adjusted all rocker arms and started the engine. The engine runs fine, steady and quiet but because of that cut in the stud, one rocker arm slides right into it and shifts to the side almost immediately unless you hold it in the position manually by hand.

I'll take off the push rod cover next and check the hydraulic valve lifters.

No, I'm not a mechanic, I'm a software developer but I've got a good friend who is machinist to help me out plus I've got the service manual and the fellow boat owners to share the knowledge When I called the shop they told me $1000 just to diagnose the issue, so trying to save the dough and learn something in the process
No water in the oil doesn’t mean no water in the cylinder.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-21-2018, 12:26 AM   #11
Commander
 
Gugi47's Avatar
 
Join Date: Apr 2018
Location: Afghanistan
Posts: 332
Send a message via ICQ to Gugi47 Send a message via AIM to Gugi47 Send a message via Yahoo to Gugi47 Send a message via Skype™ to Gugi47
Default

The stud is bend?
Find somebody who is good in TIG welding.
Make 2 hols in a 1/4x1 flat for holding the stud when welding.
But Mike is right. Take the plug out and check for water.
After yo remove the plug take a napkin role it and introduce true the plug hole 1" and hold it there. Somebody have to turn the engine 2 sec.
If the napkin get wet you have water, if not, you OK.
Good luck
__________________
If they respect you, respect them. If they disrespect you, still respect them. Do not allow the action of others to decrease your good manner, because you represent yourself not others.
-2001 Maxum 2100 SR2 Sport -1997 Regal 258 Commodore (Sold)
Gugi47 is offline   Reply With Quote
Old 05-21-2018, 11:16 AM   #12
Commander
 
jrsick's Avatar
 
Join Date: Oct 2011
Location: Chesapeake, VA
Posts: 487
Default

Quote:
Originally Posted by mmwjr View Post
This would not explain both push rods bending.
Mike, if the exhaust rod bent first then the cylinder pressure can't escape and could bend the intake valve.
1800MX, the picture looked to me like the stud had risen, sorry for the confusion.
I agree that water in cylinder is most likely cause. Gugi has good advice, and I would also recommend a borescope. You can find some inexpensive ones online. Borescope would help you locate water, see if there is cylinder head damage, and check for foreign material in cylinder.
I doubt the nick in the stud is causing the rocker to shift. Try cleaning the stud base and rocker nut, then stripe them with a marker. Start the engine and see if either shifts during operation. Rocker nuts will lose their crimp with repeated adjustments and need to be replaced.
Take this step by step and you will find the fix.
__________________
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine
jrsick is offline   Reply With Quote
Old 05-21-2018, 11:25 AM   #13
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by jrsick View Post
Mike, if the exhaust rod bent first then the cylinder pressure can't escape and could bend the intake valve.
1800MX, the picture looked to me like the stud had risen, sorry for the confusion.
I agree that water in cylinder is most likely cause. Gugi has good advice, and I would also recommend a borescope. You can find some inexpensive ones online. Borescope would help you locate water, see if there is cylinder head damage, and check for foreign material in cylinder.
I doubt the nick in the stud is causing the rocker to shift. Try cleaning the stud base and rocker nut, then stripe them with a marker. Start the engine and see if either shifts during operation. Rocker nuts will lose their crimp with repeated adjustments and need to be replaced.
Take this step by step and you will find the fix.
But the intake valve opens while the piston is going down increasing cylinder volume and pressure drops. Additionally I would think if the pressure was high enough to bend a pushrod it would blow back through the carb as soon as the valve opened. Not saying you theory is incorrect.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-21-2018, 02:51 PM   #14
Commander
 
jrsick's Avatar
 
Join Date: Oct 2011
Location: Chesapeake, VA
Posts: 487
Default

Mike,
intake valve opens just prior to TDC, when cylinder is on up-stroke. Exhaust valve has been open and escaping exhaust gases help draw in intake gases during valve overlap. If exhaust valve does not open then intake valve is trying to open against max compression.
I've seen the two bent pushrod scenario 3 times in my corvette club. In these three cases replacing the rods and setting lash fixed the problems. Causes remained mystery even though there were expert mechanics that disassembled the engines. Of course these were LS engines vice boat engines.
__________________
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine
jrsick is offline   Reply With Quote
Old 05-21-2018, 04:29 PM   #15
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by jrsick View Post
Mike,
intake valve opens just prior to TDC, when cylinder is on up-stroke. Exhaust valve has been open and escaping exhaust gases help draw in intake gases during valve overlap. If exhaust valve does not open then intake valve is trying to open against max compression.
I've seen the two bent pushrod scenario 3 times in my corvette club. In these three cases replacing the rods and setting lash fixed the problems. Causes remained mystery even though there were expert mechanics that disassembled the engines. Of course these were LS engines vice boat engines.

I accept this as plausible but would still be concerned of bent valve stems. Also the force to bend the push rod is enough to pull the rocker studs out some.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-21-2018, 07:28 PM   #16
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Default

Gugi47 and Mike, Great tips about the water in cylinder, I'll try that
Maxum1800MX is offline   Reply With Quote
Old 05-21-2018, 07:57 PM   #17
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Default

Actually the rocker arm does shift during operation and finds its way right into that nick in the stud and shifts. Also if you look at the picture closely, the exhaust valve stem on that cylinder where the rocker arm slides to the side is a bit worned out. I'm thinking of replacing it but that means the head would have to come out

Funny thing is, when I swapped the exhaust rocker arms with the intake rocker arm, it would not slide off anymore. Perhaps all I need is a new set of rocker arms?
Maxum1800MX is offline   Reply With Quote
Old 05-21-2018, 08:05 PM   #18
Lt. JG
 
Maxum1800MX's Avatar
 
Join Date: Apr 2018
Location: Vancouver, BC, Canada
Posts: 18
Default

Quote:
Originally Posted by jrsick View Post
Mike,
intake valve opens just prior to TDC, when cylinder is on up-stroke. Exhaust valve has been open and escaping exhaust gases help draw in intake gases during valve overlap. If exhaust valve does not open then intake valve is trying to open against max compression.
I've seen the two bent pushrod scenario 3 times in my corvette club. In these three cases replacing the rods and setting lash fixed the problems. Causes remained mystery even though there were expert mechanics that disassembled the engines. Of course these were LS engines vice boat engines.
Hi jrsick,
According to mechanics manual incorrect valve adjustment can cause those push rods to bent. The other odd thing I've found is that there were 2 different push rods on cylinder #3 than on all the other cylinders. Those 2 are long and have straight ends but the other 6 were new style with a little balls on each side. The 2 new ones I've got have also little balls.

Given all those worn out parts, it looks like my next option is to remove the head and replace the worn out valve (or both). Then replace both rocker arms, push rods and the sliced stud.

jrsick, looking at the pictures do you think it's necessary to replace the exhaust valve?
Maxum1800MX is offline   Reply With Quote
Old 05-21-2018, 11:56 PM   #19
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by Maxum1800MX View Post
Actually the rocker arm does shift during operation and finds its way right into that nick in the stud and shifts. Also if you look at the picture closely, the exhaust valve stem on that cylinder where the rocker arm slides to the side is a bit worned out. I'm thinking of replacing it but that means the head would have to come out

Funny thing is, when I swapped the exhaust rocker arms with the intake rocker arm, it would not slide off anymore. Perhaps all I need is a new set of rocker arms?
The rocker may have worn due that notch in the stud so just installing a replacement it may wear out in time as well if the stud is not replaced.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Old 05-21-2018, 11:56 PM   #20
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 7,793
Default

Quote:
Originally Posted by Maxum1800MX View Post
Hi jrsick,
According to mechanics manual incorrect valve adjustment can cause those push rods to bent. The other odd thing I've found is that there were 2 different push rods on cylinder #3 than on all the other cylinders. Those 2 are long and have straight ends but the other 6 were new style with a little balls on each side. The 2 new ones I've got have also little balls.

Given all those worn out parts, it looks like my next option is to remove the head and replace the worn out valve (or both). Then replace both rocker arms, push rods and the sliced stud.

jrsick, looking at the pictures do you think it's necessary to replace the exhaust valve?
You valve must be removed to tell if it’s bent.
__________________

__________________
1997 2400 SCR
5.7 Vortec / Bravo 2
Mike
mmwjr is offline   Reply With Quote
Reply

Tags
bend, bent, push rod, rocker arm, stud

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 11:47 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.