Broken Rocker Arm Stud

[sailsmanship]

I have a 1989 Searay30DB w/twin 5.7 inboards, 500 hrs. Lost power in starboard engine and when I tore it down I noticed that intake valve rocker arm stud on #7 cylinder was broke. Everything else looks fine and I can't see anything that might have contributed to it. Could this possibly be a freak thing or am I just not seeing something. Is there anything to look at that might be the underlying cause.

 

[lowshovel1]

Re: Broken Rocker Arm Stud

have you pulled that head yet? It may have been just a freak thing like you say.BUT if it were mine I would pull that head and check it out.

 

[lowshovel1]

Re: Broken Rocker Arm Stud

did it break off flush with the head? or up higher from base of stud?

 

[achris]

Re: Broken Rocker Arm Stud

You don't say what breed of engine you have. However, #7 cylinder is a rear. When were the exhaust elbows checked/replaced? If you have a leaking elbow, then water could have gotten into the cylinder and cause the stud breakage. Like the previous poster suggests, remove the head and have a look around. <br /><br />Chris.......

 

[sailsmanship]

Re: Broken Rocker Arm Stud

It' a Mercruiser, And I have pulled the heads.They look fine but what I did notice when I took off the exhaust manifolds,is that side did not have water running out, while the other side did. Maybe it was leaking in.Also the stud busted up higher not flush...

 

[Bt Doctur]

Re: Broken Rocker Arm Stud

Only way i know to break a stud is to have a valve stick or jam up .either bends/breaks the push rod or the stud.

 

[FreeBeeTony]

Re: Broken Rocker Arm Stud

What were the symptoms of the engine? <br />How was it running?

 

[Olds Eddie]

Re: Broken Rocker Arm Stud

Those engine have press in studs. I would have them replaced with screw-in studs while I had it apart. They are recommended for any performance modifications to this engine. ARP studs will not break.

 

[sailsmanship]

Re: Broken Rocker Arm Stud

I bought it at auction and while I was driving it home I thought the engine cables needed to be sync'd since the one in question needed to be way far foreward in order to match rpm, but it would not go over 3400 rpm. The really wierd thing was that at idle and no load rev it purred like a kitten and since I have a flybridge I could really could not hear it struggling. I have had alot of engines in my lifetime and I never had one give me a false reading like this. It was really a trooper given she was working with one paw tied behind her back.

 

[KaGee]

Re: Broken Rocker Arm Stud

Hey Sail!<br /><br />Take the head over to Aarons over on Sylvania or to the guy in Maumee.... I forget his name right now, to have it checked out and repaired.<br /><br />Glad to see another fellow boater from the area on Iboats!<br /><br />Better check those manifold/riser/gaskets for maintenance or replacement. The water is not a good sign.

 

[rayjay]

Re: Broken Rocker Arm Stud

It is not unknown for SBC's to break a stud. If you look at the break you will probably see that the stud was cracked and eventually broke completely. Usually happens right at the bottom of the threads.

 

[FreeBeeTony]

Re: Broken Rocker Arm Stud

How did you determine it was a broken rocker arm stud?

 

[Limited-Time]

Re: Broken Rocker Arm Stud

FBT,<br />

Originally posted by sailsmanship:<br /> Lost power in starboard engine and when I tore it down I noticed that intake valve rocker arm stud on #7 cylinder was broke.

If your still chasing your graemlin the Vaccume test you preformed should have indicated a stuck/closed intake.

 

[FreeBeeTony]

Re: Broken Rocker Arm Stud

I was just wondering what type of troubleshooting he did before he took off the valve covers...<br /><br />I thought about the vacuum test.......how much would it drop if 1 intake valve was not opening?

 

[sailsmanship]

Re: Broken Rocker Arm Stud

When we started to check the engine we pulled the plugs and he said something on #7 was amiss. put new plugs and cap on (just because I wanted to) and put a tester on it and determined it was not an electrical firing issue. Then did a compression test and found 20lbs. on that cylinder. Then removed valve cover and seen the broken stud.

 

[Don S]

Re: Broken Rocker Arm Stud

Tony<br />A broken rocker arm stud would cause one he11 of a miss in the engine, a dead cylinder.<br />This is not your problem, (NO Misses, according to your previous posts) you have a restricted exhaust, you just don't know it yet because you won't get the boat out of the water to find it.

 

[FreeBeeTony]

Re: Broken Rocker Arm Stud

Don, I'm on my way to getting the boat out of the water........I am selling my other boat this w/e, then I am going to buy a trailer and pull this one out and take off the drive to inspect.<br /><br />I couldn't have 2 boats in my driveway at the same time! <br /><br />I sure hope you are right about the exhaust restriction! You will be the first to know!