3.0 Mercruiser Gasket Materials/Torque Specs/Use Sealant?

[josephr93]

Putting my 1991 3 liter mercruiser back together after having water in cylinder 4. I actually have two different gaskets for the exhaust riser. One is out of the Sierra 18-4367 set and the other is 18-2833-9. The 2833 is a shiny silver and the 4367 is a dull gray.
1. What materials are these/what are the differences between these?
2. Does the torque spec differ for these? My manual states 20-25lb ft as the torque spec, but I have also seen a lot of people stating 33 lb-ft.
3. My boat is in fresh water only, the surfaces for the riser gasket are relatively clean, but it appears someone before me used a very aggressive tool for removal and as a result there are deep-ish (~0.5mm) gashes that cross from the water jacket to the exhaust. Would it be advisable to use something like perfect seal in addition to the gasket? I understand the factory start with not sealer, but given the reality of this situation/imperfect surfaces? Can this sealer interact with the gasket in any negative fashion?

 

[alldodge]

Exhaust pipe and elbow 20-25 ft lb
Exhaust manifold 23 ft lb starting in the center and working out. Run motor up to temp and re-torque

The 33 ft lb is used on other motors not yours

Having a 0.5mm (0.019) is deep, spec says (in other manual) 0.0762mm (0.003)
May need to be machined, or could try a flat file across the surface

Manual 13 (your motor) does not list high temp gasket to be used only the gasket.

18-4367 is a gasket set
18-2833-9 is a elbow gasket which is part of the set

One being shinny and other being shinny would indicate some metal in manufacture

 

[alldodge]

Later manuals list Loctite 510 to use on flanges

 

[josephr93]

alldodge, thanks for responding. do those later manuals say use 510 alone as a gasket, or to put a bead of 510 on both sides of a gasket then assemble? im thinking i might pick up some 510, these gashes in the surface are pretty deep. in any case im going to be religiously peaking in spark plug holes for water for a while after this. $140+ for a new riser is out of the question/ this boat/engine/drive is at the end of its life and gets shoestring repair only

 

[alldodge]

The sealant is used with the gasket

 

[QBhoy]

Hi
in addition...just make sure you are torque it down when it’s evenly face to face with the opposing flange. Very easy to get a false feeling of tightening depending on how much of the outlet pipe you have into the rubber sleeve to the down pipe. Leave that loose. Stand on the bugger if you have too. Those bolts are easily broken. Get some copper slip or similar grease on the threads.