Mercruiser 7.4 - exhaust manifold problems

[Deanman77]

Hi,
I'm new to the forum and need some advise. I have a Bayliner 2855 Bravo III- 1998 I,m the original owner and have used very little - has less then 150 hours on the meter. I pulled the risers and they are gone - my problem is the manifolds are very, very rusty on the bottom - the heads of the bolts are gone.
We started drilling a line down the center of the manifold and using a baby sledge hammer busting away the manifold (or I should say attempting too) - It's not working so well - maybe I'm not hitting it hard enough??

What is your suggestions on the best approach to get these off - I've just finished replacing the seawater pump and the water circ pump -

Please help - and I know that pulling the engine is a good option, but this boat has a radar arch - and looking at the engine today I don't think it will fit through the opening without 1 removing all of the front end parts, or 2 turning it sideways on the way out. Very small engine opening......

I'm hoping for advise excluding pulling the engine - any Ideas???? I'll be glade to get any advise - after beating on this thing for an hour there has to be a better way.


Thank you
Tim

 

[dubs283]

Re: Mercruiser 7.4 - exhaust manifold problems

grind the bolt heads off then use a stud remover/penetrating oil/heat to remove whats left of the bolts

 

[Deanman77]

Re: Mercruiser 7.4 - exhaust manifold problems

grind the bolt heads off then use a stud remover/penetrating oil/heat to remove whats left of the bolts

Thanks - that is my plan when I get enough of the manifold out of the way to get to the bolts - can't see the bolts at all

Have you ever removed a manifold with a hammer - or cut it with some type of tool?? I'm just worried about hitting it too hard - could this cause other problems?

Thanks
Tim

 

[dubs283]

Re: Mercruiser 7.4 - exhaust manifold problems

Have you ever removed a manifold with a hammer - or cut it with some type of tool??

only once, the motor was out of the boat, ground off the bolt heads, etc.

i wouldn't hit any part of an engine with a hammer

 

[Deanman77]

Re: Mercruiser 7.4 - exhaust manifold problems

Would pulling the heads be a reasonable option???

Then remove the manifolds on the bench??

I do have a plasma cutter - not totally safe, but better then a torch.

I have also considered using a cutting wheel on a grinder to remove enough of the manifold to get to the bolts - whould the grinding fragment cause other issues?

Thanks
Tim

 

[HT32BSX115]

Re: Mercruiser 7.4 - exhaust manifold problems

Howdy,


If you can get to both sides of the engine with a small grinder you can grind the heads of the bolts off or center punch each and drill them off. That'll leave about 1/2" or so of bolt when you pull the manifolds off.

Then you may be able to use a 6" pipe wrench or vise grips to pull each bolt.

HOPE AND PRAY you don't break them off. If that happens, you'll be drilling them and extracting them with an eze-out or similar extraction tool.....


Cheers,

Rick

 

[wschmitt]

Re: Mercruiser 7.4 - exhaust manifold problems

Yes i have drill and pounded with a hammer for 6 hr and hit the manifold hard as i could finally it started to break up dont be afraid of doing any damage to the head you can always fix the head or change it the other side i am thinking of useing a grinding wheel on my 4'' grind the blade is for metal have you try that before i start i wont to know if that work's

 

[Steve Cook]

Re: Mercruiser 7.4 - exhaust manifold problems

I got as many bolts out as I could (not many)
then I got in there and kicked the riser outward as hard as I could, the manifold snapped off like nothing
I chisled away the remaining bits of manifold that were hung up on the remaining bolts
most the bolts snapped off flush at the head
I just got busy drilling then using an easy out screw extractor, that worked on about half
the rest I finally drilled completely out with a 5/16" bit and ran a 3/8" 16p bottom tap through it
2 days of intermittent work... done deal