7.4 Merc motor mount stringer bolts won't back out

[MightyEsquilax]

So...I'm trying to replace my rusted front motor mounts on my 7.4 Merc. I can freely turn the lag bolts on the port and starboard side motor mounts and they won't back out for me. I've tried prying on the washers with a screw driver and even carefully tugging with some channel lock pliers but I don't have a lot of room unless I take out the exhaust manifolds which I was hoping to avoid. Any good lag bolt removal tips or tools anyone can recommend that work well in a tight space? I can turn the bolts fine I just can't get them to back out.

Thanks for the help!

 

[alldodge]

You need to remove the motor. Even if you get the bolts out, using larger ones will not fix an issue which will cause the mount to sink further. Remove the larger nut on top the mount and pull the motor, then rebuild the mount

 

[MightyEsquilax]

I'm trying to avoid removing the motor. The nuts on both mounts are rusted and don't move. That's why I'm supporting the engine with a jack and removing the mounts to replace them so I can align the engine correctly. I did this same process on my 4.3 but in that case the lag bolts backed out as expected. These lag bolts won't back out. I didn't know if there was a tool or recommend method that could help.

 

[Bt Doctur]

miniature crow bar

 

[tpenfield]

If the lag bolts spin freely, but won't back out, I am wondering about the condition of the motor mount stringers. :noidea:

Maybe you will be taking the engine out . . .

As for the motor mounts themselves, with rusted bolts, etc. I have been there, done that and ended up supporting the engine with a scissor jack under the exhaust manifold while I detached the whole mount & strut from the engine block. I had to cut the nuts off of the mounts to free the struts from the engine mounts. . . . new engine mounts of course.

I did one side at a time to reduce the risk of the engine falling off the scissor jack.

 

[Bondo]

If the lag bolts spin freely, but won't back out, I am wondering about the condition of the motor mount stringers.

Ayuh,.... Ditto Ted,..... If the motor mounts are rotten, a PO mighta poured epoxy into the holes, 'n dropped in the lag bolts, which are now bonded to the bolts, 'n the rotten holes are even bigger,...

By pullin' the bolts from the block, ya might be able to roll the whole mount out,...