1990 Mercruiser 5.7/v8 rusted exhaust manifold bolt

[landover50]

I bought a Bayliner 22' capri earlier this year. I knew the manifolds needed to be replaced. During my winterizing I realized one of the manifold bolt heads is severely rusted. This is going to be a job for the spring but want to get a plan off attack for when I dive into it.

What is going to be the best way to get it and the manifold out? I've read a bit but want to see what suggestions I get here.

 

[Scott06]

Lots of heat at the base would be my first attempt that not working the head will break off or cut it off with a grinder so the manifold can come off, if us are lucky you will have a headless bolt sticking out , more heat penetrating oil pipe wrench or vice grip on shaft of bolt sticking out of head. If it breaks off flush ... easy out, worst case remove head drill out and retap on bench or at machine shop...

don’t know why they call them easy outs... every time I have to use one it’s a PITA

 

[landover50]

Lots of heat at the base would be my first attempt that not working the head will break off or cut it off with a grinder so the manifold can come off, if us are lucky you will have a headless bolt sticking out , more heat penetrating oil pipe wrench or vice grip on shaft of bolt sticking out of head. If it breaks off flush ... easy out, worst case remove head drill out and retap on bench or at machine shop...

don’t know why they call them easy outs... every time I have to use one it’s a PITA

Good advice. I think I might run into an issue if I have to grind the head off. I only have a couple inches lateral space to move the manifold out. I don't think I'll have enough space to get the manifold all the way off of the bolt.

 

[Rick Stephens]

A lot of heat on the head. Let it cool completely - the heat expands the bolt to break loose the corrosion, the cooling lets it shrink back. Then use a socket designed to remove damaged bolts.

Anyone who welded up a manifold like that did other lazy or hairbrained stuff. Make sure you go through everything.

 

[landover50]

A lot of heat on the head. Let it cool completely - the heat expands the bolt to break loose the corrosion, the cooling lets it shrink back. Then use a socket designed to remove damaged bolts.

Anyone who welded up a manifold like that did other lazy or hairbrained stuff. Make sure you go through everything.

View attachment 328585

Thanks for the input. the guy I bought from said it was welded up like that when he bought it 20 years ago and he's just let it go. Both manifolds are actually welded up and leak. Lots of corrosion, rust, and hard water build up on both sides. I'm sure I'll be posting again once I get into it to figure out other issues I find.

Where is the best place to get replacement manifolds?

 

[kenny nunez]

The first thing I would do is to pull the engine since there is not enough room in the boat to remove the manifold and I bet that the oil pan and timing cover are on life support.
One trick that works for me In that area is to get a hole saw that will fit closely over the rusted bolt without the drill bit and cut almost to the head surface. The remaining material will easily break away and hopefully the rest of the bolts are not rusted solid in the manifold.

 

[Lou C]

And if the manifolds were welded up (freeze damage) I wonder if you will find JB weld patching freeze cracks on the side of the block...because if someone let it freeze and the manifolds cracked, the engine might have as well.
Is the oil clean, or milky?

 

[landover50]

And if the manifolds were welded up (freeze damage) I wonder if you will find JB weld patching freeze cracks on the side of the block...because if someone let it freeze and the manifolds cracked, the engine might have as well.
Is the oil clean, or milky?

Oil looks great. He said he's been running it like this for years, and you can tell due to the hard water buildup on the manifolds, so I imagine if there were water getting into the block it would have causes issues by now?

 

[Lou C]

Yep you’d think so as long as no water in the oil or cylinders it should be ok

 

[Scott Danforth]

with a die grinder, cut the head off. then when you remove the other bolts, slide it off the remaining portion of the bolt. then with a pair of vice grips, remove the bolt

 

[landover50]

with a die grinder, cut the head off. then when you remove the other bolts, slide it off the remaining portion of the bolt. then with a pair of vice grips, remove the bolt

Thanks for the tip. I think I might run into issues getting the manifold off the bolt. I only have a few inches lateral movement away from the engine to slide the manifold out.

 

[Scott Danforth]

looking at the manifold, I would simply cut thru the manifold and the bolt and get new manifolds.

 

[landover50]

looking at the manifold, I would simply cut thru the manifold and the bolt and get new manifolds.

Definitely getting new manifolds, hadn't thought of just cutting them off. Any special tricks or just go at it with a grinder?

 

[Scott Danforth]

Cut-off wheel in an angle grinder