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broken studs 1980 120 hp merc

I

iwish

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i ave a 1980 120 hp mercruiser and wile driving a strange noise appierd after investigation found 2 broken studs on manifold so i drilled them out replaced them wit new plus new gasket 2 days later 2 same studs broken again those are the back studs neer exaust elbow i think will need help i dont understand.svp
 
Re: broken studs 120 hp merc

iwish said:
i ave a 1980 120 hp mercruiser and wile driving a strange noise appierd after investigation found 2 broken studs on manifold so i drilled them out replaced them wit new plus new gasket 2 days later 2 same studs broken again those are the back studs neer exaust elbow i think will need help i dont understand.svp
Click to expand...

did you use torque wrench ? how much torque ?
 
Re: broken studs 120 hp merc

So you didn't remove the mani and start fresh with the torque center out ?

Did you consider that the mani warped. You didn't consider removing the riser and torquing.

There are kits, new bolts, gaskets everything you need.

What else is going on with the motor ?

Did a event happen ? Like a overheat that you didn't post ?

I know that motor better then the back of my hand, so tell us everything.

When you got it, everything.
 
Re: broken studs 120 hp merc

the studs broke at the same spot flush in the block, and yes i did remove the manifold and put a new gasket .mani fits nice and snug does not look warp to me, but i will check . ok now i ad this for over 2 years ran ok .as for changes re did timing ,adjusted points,changed prop from a 19 pitch to a 17p due to lack of power to pull out a skier fast.by the way the max rpm was 3900 and now 4400 close 4500. could the mani water portion be blocked a bit causing overheat at the mani .the prop was changed one week before, and i was pulling my son on skis wen it blew, rpm was a bit over 3500.
 
Re: broken studs 120 hp merc

What sequence are you using to tighten down the studs.

When you have it off make sure it's true the mani mating surface.
 
Re: broken studs 120 hp merc

what rubber ?

Your welcome.

What i do is chase all the holes. Then i get 2 extra long bolts cut the head off "Actually the ones i have maybe 20 years " And turn them into the 2 end holes. Hand tight.

Then i slip on the mani on those 2 end bolts. Install the middle ones hand tight, then turn off one end install the stud, and twist off the other install the bolt.

I would first buy the kit, get a can of aviation form a gasket, and check for true on both mating surface, paint both sides of the gasket, slip the gasket on first with the end extra long bolts in and then the mani, and do the do.

Thats it.
 
Re: broken studs 120 hp merc

wen i remove the mani ,the elbow is attached to sum sort of rubber donut wit 2 hose clips exhaust out .that rubber .dont it take a lot of force to brake 3/8 studs ? there as to be some thing wrong,considering that at first event studs could be original .
 
Re: broken studs 120 hp merc

wonder if the engine mounts could be a problem? and not sure what you mean by chase all the holes
 
Re: broken studs 120 hp merc

iwish said:
wonder if the engine mounts could be a problem? and not sure what you mean by chase all the holes
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chasing the threads means using a thread taping tool to insure the threads are clean and true. then blow out any rust / old thread sealants.

the exhaust elbow is connected to a rubber bellows that should separate the engine from the exhaust tube to the drive. is this elbow resting on the exhaust tube ?
 
Re: broken studs 120 hp merc

will be working on the boat by the end of the week. am i the only one who ever ad that problem ? in life it feels good to help.s.v.p. make yourself feel good .need the help ,i will pass it on.
 
Re: broken studs 120 hp merc

ok I cat thanks, i did that, threads are good .studs break flush to the block then i use a extractor to unscrew them out .but how come they break in the first place?
 
Re: broken studs 120 hp merc

iwish said:
ok I cat thanks, i did that, threads are good .studs break flush to the block then i use a extractor to unscrew them out .but how come they break in the first place?
Click to expand...

if the exhaust elbow is hitting the exhaust tube this is not correct ..the bolts will get stressed out . check the engine mounts if it looks even a little off or messed up do the engine alignment . I never seen this . perhaps the chief has a better handle on this one .
 
Re: broken studs 120 hp merc

and like chiefalen says.i will check for true, thanks .someone as an id tell me, will consider .
 
Re: broken studs 120 hp merc

is there a 4 by 6 inch rubber tube connected to the riser on one end and the exhaust metal tube on the other. The elbow should not touch the metal tube. If it does then they make a spacer goes under the riser.

But that should not be needed, the exhaust tube connected on the bottom ?

People you think the motor dropped that mush he would never move would bind the shaft no ?

Should he pull the drive and use a alignment bar to find out for sure?

And if it did drop half the work is done cause you got to pull the drive first anyway, to pull the motor.
 
Re: broken studs 120 hp merc

yes there is a rubber tube,size cant tell now,the idea about spacer could maybe solve this, but that could mean the engine mounts are bad,and putting pressure on gimbal bearing .i just might be getting closer .?where can i get a alignment bar and how much is that tool worth ?thanks chief, maybe, i could finish the season with a elbow spacer, so my kids can enjoy boating and wen i pull it out of the water dad gets to work again .mounts ,what should i look for? ave a good day all.
 
Re: broken studs 120 hp merc

ok i am up north, will be working on the boat in the morning. orderd gaskets for the mani, elbow, end caps. ho, chief tried to get spacers for the elbow and the dealer says not available, if you ave a part number?i intend to make a spacer out of 1/8 aluminium maybe put 2 spacers what do you think?
 
Re: broken studs 120 hp merc

well did work on the boat , after inspection, the rubber tube is very compresd it seems the mounts are siting low so i imagine there is alot of pressure on the shaft and gimbal bearing,so i probably will remove the drive change bearing, joints, alignment .but i will try to end season by using a spacer on the elbow, (riser)so i made one today out of 1/2 inch aluminium, waiting for gaskets.cross my fingers,i will post if it works or not.alingment bar someone knows how to get and how much cost?
 
Re: broken studs 120 hp merc

ebay maybe 50 bucks delivered. Listen no way you can jack up the rear mounts, and place something under the mount to get thru the season when you get the bar?

See that drive and coupler isn't aligned perfect your gonna blow the coupler.

Where up north ?
 
Re: broken studs 120 hp merc

ok reinstalled the mani ,spacer on , hope for the best ,will see. thanks to all of you, Norm, i will post.
 
Re: broken studs 120 hp merc

Tried the boat, ran good, came back (dock), removed the in line filter, started the engine - pop noise - ,checked studs... ...one is missing, oh my god. Seems the force is not with me. Should i just sink the boat (ha..ha). The stud that went, well, is not the same, now I have to drill and use easy out, what a job???
 
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