Manifold bolt rust

jmauld

Well-Known Member
Jun 9, 2020
2,843
Carolina Beach
Boat Info
2010 Sundancer 390
2016 Sea Hunt Ultra 211
Engines
Twin 8.1l of gas guzzling iron
I have done two of my four manifolds so far, and I removed the third one last night. This one had a single bolt with rust on the shaft of the bolt and when I removed it, there was a small amount of water in the bolt hole. (I wasn't brave enough to taste the water since my fingers were so greasy)

How worried should I be about this?
 
The install guidelines do say to use sealant on the bolt threads. Which seemed odd to me.
 
Last edited:
How so? There're blind holes

My Crusader elbow studs have threads that are open to the water jackets and require thread sealant and the stud threads. I also put anti seize on the studs to aid in future removal of the elbows and fresh water adaptors.
 
Mercruiser Perfect Seal is great stuff.

Not only is it a thread sealant, but acts as an anti size compound as well.
..and it’s like mustard and seems to get everywhere.
 
upload_2022-8-7_14-52-3.png
 
The water behind that and several other bolts is normal. Several of the holes are deep enough to enter the water jacket of the block. All that water was, was a cooling fluid that didn't completely drain out prior to removing that bolt, absolutely nothing to worry about. Before reassembly use a tap and die to clean the threads of the hole and bolt so you can get a proper torque reading during reassembly. Use thread sealant not anti-seize during reassembly. The lithium in anti-seize is a base metal and with the contact to the water jacket can expedite electrolysis. The Teflon in the thread sealant will be adequate to act as an anti-seize plus its what is advised in the manual.
 

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