Exhaust Manifold Removal and Replace

[wewefirex2x]

I just bought my boat June 2006. 1989 Monterey Cuddy 5.0 Mercruiser, Alpha One. The boat was kept in a wet slip during the summer with evidence of corrosion in thermostat housing. I get plenty of water flow through exhaust.

I would like to take my manifold and risers off to inspect. I have been told that I should not remove them myself. I was told if I remove them I am almost gauranteed to break a manifold bolt. If a shop removes manifold and breaks a bolt that have to remove the broken end and replace (of course I get charged labor and material).

1. Is there an easy way to remove manifold without breaking bolt?
2. If I break a bolt, how easy is it to remove?
3. Would you do this manifold yourself?

 

[JustJason]

Re: Exhaust Manifold Removal and Replace

instead of removing them... go out and buy an ifrared pyrometer. (temp gun) like a raytek. go run the boat around the lake a few times, bring it back to the dock and pull the hatch cover and scan the manifolds and risers. 120 - 140F are good numbers. If your up over 160 then replace the manifold and riser. 1 side will usually read about 10F hotter than the other, that is normal.

 

[Haut Medoc]

Re: Exhaust Manifold Removal and Replace

I just bought my boat June 2006. 1989 Monterey Cuddy 5.0 Mercruiser, Alpha One. The boat was kept in a wet slip during the summer with evidence of corrosion in thermostat housing. I get plenty of water flow through exhaust.

I would like to take my manifold and risers off to inspect. I have been told that I should not remove them myself. I was told if I remove them I am almost gauranteed to break a manifold bolt. If a shop removes manifold and breaks a bolt that have to remove the broken end and replace (of course I get charged labor and material).

1. Is there an easy way to remove manifold without breaking bolt?
That will completely depend on the amount of corrosion on the threads.......
Try them first & if they do not want to move apply some heat & cool it quickly......
2. If I break a bolt, how easy is it to remove?
That depends on where it breaks....
Worst case scenario is drilling & an EZ out....
3. Would you do this manifold yourself?

Yes, it is not that hard, & I would use anti sieze on the threads when you put them back on......

 

[wewefirex2x]

Re: Exhaust Manifold Removal and Replace

Thanks, nice tip about the infared. I guess that would give me good indication of the life left of manifolds.

 

[Bondo]

Re: Exhaust Manifold Removal and Replace

I guess that would give me good indication of the life left of manifolds.

Not Really...............

It'll tell you if they're Plugged up,.......
But,......
It Won't tell you that they're Rusted thru,+ are about to dump Seawater into your motor............

 

[Chris1956]

Re: Exhaust Manifold Removal and Replace

The good news is that the exhaust manifold bolts are protected from the cooling water, so they are not usually rusted in the manifold or block. The riser bolts can be rusted into the manifold, but I have found that the good grade of steel in these bolts holds up pretty good. I was able to disassemble my 12 year old risers w/o breaking any bolts.

 

[wewefirex2x]

Re: Exhaust Manifold Removal and Replace

Thanks for the encouragement Chris. Bond-O I spoke too soon before thinking.

 

[JustJason]

Re: Exhaust Manifold Removal and Replace

the manifold to block bolts come pretty easy... its the riser to manifold bolts that always freakin break.

Not Really...............

It'll tell you if they're Plugged up,.......
But,......
It Won't tell you that they're Rusted thru,+ are about to dump Seawater into your motor............

very true... i think alot of it is location. when i was in fl manifolds failed more often by rotting through. if you were lucky enough the boat would be misfiring like crazy and you'd catch it before any damage was done.
up here in ma, and i'm going to suspect most northern states, i see more that are clogged up than anything else.

 

[njlarry]

Re: Exhaust Manifold Removal and Replace

If I can do it in 45 minutes, anyone can (if the bolts don't break). But even if they do there's a lot of room to remove them. Get the right OEM manual. some spray on gasket remover, check for warpage with a sraight edge and feeler gage. Install with antisieze and a torque wrench and retorque after about 20 hours.
(My volvo reguires that NO gasket sealer be used but your Merc may be different.)
As said above, in salt water you should check them very couple of years anyway.

 

[desi]

Re: Exhaust Manifold Removal and Replace

I agree with Bond-o and Chris 19??, There are several things that could be wrong with your manifold at that age and stage. The bottom line is to have it pressure tested to see if it not putting water where it does not belong. If you are inspecting it for currosion and not because it presents a problem of some kind are another then the obvious applies as to what to look for. If currosion is a problem then you will need another riser as well. If you have twin screws you can look to change the other one soon after. Another thing you may want to check is if the face of it is warped.In which some cases you may see water/rust stains down that side of the block underneath the manifold.
Generally speaking if it is curroded to any extent, don't take any chances with it having a blow threw and ending up with water on top of your piston as Chris 19?? mentioned. I recently seen these problems with my Volvo.