88' 3.o mercruiser exhaust manifold bolts

[forplayboat]

This is probably a stupid question but I will ask it anyway. I have an 88 3.0 liter mercruiser that is run exclusively in salt water. The exhaust manifold and riser(elbow) are toast and need to be replaced. I purchased the parts and gaskets and i am ready to replace the parts. one of the heads on the bolts that go through the manifold securing it to the head is so rusted that I cant get a wrench to bite to get the whole thing off. I thought about taking an angle grinder with a cutting wheel and cutting the head of this rusty bolt off and pulling the manifold off with the majority of the bolt still in the head and then removing the remainder of the bolt with vise grips or whatever works. Does any one have any comments on this proposed procedure. Do you think it will work??? I have been out of the water for way too long(3 weeks)and I need to do this repair before I can get back out. Any comments or suggestions will be very much appreciated. Thanks, Jim.

 

[Bondo]

Re: 88' 3.o mercruiser exhaust manifold bolts

Ayah.....<br />That's the Way it's Done............

 

[elpaso]

Re: 88' 3.o mercruiser exhaust manifold bolts

Have you tried to use an under size socket and hammer it on.<br /><br />If you do not have the space for a grinder, you can drill the head off. A pain but it works.

 

[bbracken]

Re: 88' 3.o mercruiser exhaust manifold bolts

I agree with elpaso, try a millimeter or /32 size socket which barely fits and hammer tightly. Don't try to turn it until you have it firmly in place. Use a 6-point socket, not a twelve-point. Also, grind 1/16 off the end of the socket so it's flat or slightly slanted toward drive end. Sockets have internal slant or rounding put there by someone who never used one. It eliminates 20-30% of potential grip area, but looks pretty in the store. I do this with all my sockets.<br /><br />Do not cut or drill unless you absolutely have to. I doubt if you will get more torque from vise grip. If you do drill start with 1/16, taking great pains to get in center. Increase drill size gradually until near threads, then use EZ out.<br /><br />When you put new bolts in coat threads with copper based never-sieze.

 

[bbracken]

Re: 88' 3.o mercruiser exhaust manifold bolts

Another thing which sometimes helps. If you have a moto-tool, use a thin cutoff wheel to cut slot in bolt head. Put a box wrench (ground flat, like I said above) on hex and have someone else apply torque with big screwdriver while you apply wrench.<br /><br />BTW I just changed manifold on my 5.7L and established bill's one-bolt theorem: "Any object fastened to an engine with n bolts, will always have exactly one bolt which is any or all of: inaccessible; frozen, or otherwise impossible to remove by ordinary mechanical means."<br /><br />The "blue wrench" is not ordinary mechanical means and is not recommended for close quarters in marine environment.

 

[forplayboat]

Re: 88' 3.o mercruiser exhaust manifold bolts

That's funny. Unfortunately it is also the truth. Thanks all for the tips. It seems easier to grind the head off the bolt in about 2 minutes to me. I have plenty of room to work. I'll re-post with the results.