Taking rusted manifolds off Merc 7.4

[videorov]

The bolts are rusted, spark plugs rusted. Need<br />to get the manifolds off and spark plugs out?<br />Any ideas on tools needed to do the Job and<br />the way to do it?<br />Im going to put stainless risers back and aluminum manifolds with closed water system.<br />The motor is around 2 years old out of a Baha.<br />I got the old risers off no ploblem but the rest<br />is going to take some work.

 

[conimicut1]

Re: Taking rusted manifolds off Merc 7.4

You can try soaking the manifold bolts with penetrant frist, but they are so long I doubt if it'll help. Take the manifolds off first, you'll get better access to the plugs that way. If you've rounded off the bolts and the manifolds are trash get a torch and torch the bolt heads off and slide off the manifolds, make sure you get all the bolts! Then heat up the heads where the bolts go into the head and work out the remainder of the bolts with a vise grip or a stud tool. Now if you have the motor on a stand try and turn the motor on its side and soak the hell out of the one side of plugs with penetrant for a few days and then try. <br /><br />However, it sounds to me that this block may be too long gone to rebuild, most marine blocks are considered to be too far gone to rebuilt. It may not be woirth all this effort, check prices for a rebuilt outright. Manifolds and risers in a rebuild are junk as a matter of fact, replace them all too. Another suggestion, if its getting rebuilt just take off the manifolds and drop off the heads with the spark plugs still in them at the rebuilder for him to check out, he may say they are junk and start fresh.

 

[videorov]

Re: Taking rusted manifolds off Merc 7.4

The motor runs great. I saw it running in the Baha when I bought it. But just under the manifold there was rust on the bolts and sparks.<br />The rest of the motor is real clean. When the guy washed down the motor all the time looks like he didn't wash under the manifolds good.<br />Yea Harbor has a 4 wheel heavy duty stand. I lake the 4 wheel too. I will check the other companies too.<br />Once I get these parts off I think it will be fine. I wonder if guys used stainless bolts on manifolds. Thats what I would like to use.<br />Stainless everything and anti seize.

 

[snapperbait]

Re: Taking rusted manifolds off Merc 7.4

Take a wire brush on a drill and brush off as much rust as you can... Head down to the autoparts store and pick up a can of PB Blaster... It's like wd40, but better...<br /><br /> Soak everything with PB Blaster a few hours before you start dis-assembly... Just let it work itself in.. Then, just before you start removing all the bolts and plugs, spray em' all down again... <br /><br />Better living through chemistry..

 

[akriverrat]

Re: Taking rusted manifolds off Merc 7.4

i ended up knocking all the rust scale off the manifold and head bolts and having them a size in between. hammered on metric socket that was just a hair under. actually used 3 different sizes. to keep aluminum corrosion from locking the shank of the bolt in the hole through the manifold i grease the whole ss bolt up. it stays trapped between the bolt head and the head. real easy to get the manifold off 2.5 years later. the best advice i've seen on this forum is "any grease is better than no grease." bondo's signature line.

 

[loadnet]

Re: Taking rusted manifolds off Merc 7.4

I removed a rounded frozen rusted bolt in this manner once.. maybe this will help you or someone else out.<br /><br />I ground down the head of the bolt so there was nothing left but the diameter of the stud showing, then positioned a new nut over the end of the stud.... and mig welded it in place.<br /><br />Once it cooled down real good I then removed it with the next size larger socket up from the original.. no problem.

 

[videorov]

Re: Taking rusted manifolds off Merc 7.4

That sound like a good idea. Ive been thinking along that line to get them out. I didd something<br />like that one time to get a bolt out of a pulley puller that got stuck and it works.<br />I might have to take the heads off to get enough<br />of the bolt to stick out.<br />I might get the spark plugs out better with the heads off.<br />I haven't started it yet. Im in the process of buying a engine stand for it so I can work on it.