Re: Sealer for Mercury crankcase halves

[Pete]

quote Wedgie:

I used this on my Mark 28 project and it worked well. Permatex makes an activator to use in conjunction with this anaerobic sealant, but it is not necessary unless you are in a hurry. I’m sure the 847 will work just fine though.

https://www.permatex.com/products/gaske … e-sealant/

https://www.permatex.com/products/threa … naerobics/

These are good products. For my split case Mercs I use the Permatex anaerobic gasket maker (link follows), basically the same as the Locktite 518 product, but the flange sealant would also be a good choice it is a little thinner. I use a "very thin" application of the sealant on both surfaces with very minimal squeeze out when tightened. If case and block surfaces are true and flat all that is needed is a very thin amount to seal. When I apply it the surfaces look slightly red tint. I do not lay a bead of the sealant, I lightly finger dapple it on and spread it out on the surfaces.
The activator speeds curing if you need to use the engine about next day. I never use it for additional work time and my rebuilds sit for days before start up. The activator does add additional strength to the bond.

https://www.permatex.com/products/gaske … ket-maker/

The split case engines are line bored with the case installed without any sealant therefore the thinnest amount of sealant is best to keep the tolerance of the line bore. I always check the flatness with machinist rule up all seal surfaces and across the split case and block surfaces with a back light. If light is visible I true the surfaces till flat in both directions for the case and the block. The engines I have worked on required no more than a light resurface to remove less than 0.0005" (1/2 a thousandth). Cases usually need truing near the bolt holes. The resultant clamp fit of the reed cage is a bit tighter and that is a plus. If the surfaces are not true I have seen the sealant fail on split case engines.

When reinstalling the case and getting the bolts in place I keep it slightly separated from the block to prevent curing too soon, then when ready to tighten I close the case to block and tighten bolts with correct sequence, 3 steps of torque. I also keep the bearing caps slightly up and snug down after 1st tighten pass of the case bolts. Last bolt to tighten is the reed cage lock bolt.

Not familiar with 3M 847 which is a nitrile rubber formulation that might leave too thick a layer of sealant ❓

http://multimedia.3m.com/mws/media/6698 … 7-847h.pdf

The Loctite Master Gasket Sealant is probably the same as the Loctite 518 which is essentially the same as the Permatex product I linked above.