It is not all that hard to replace a set of exhaust manifolds on a Chevy-based marine engine.  

1. Remove the hose clamps that connect the riser to the exhaust


2. In this case we had to remove the oil filter on the port side


3. Remove the bolts that hold the riser and the manifold on


4. You migh have to use a screwdriver or something similar to pry the manifold loose.


5. Use a lond stud on the two outside bolt holes and you can slide the new gasket and manifold on with no fumbling after of course you remove any leftovers from the old gasket on the engine block.


6. Put the new gasket on and then the new manifold


7. Tighten the manifold bolds beginning with the inner bolts first (all 27 N.m/ 20 ft-lb) and then the riser bots (all 27-34 N.m/20-25 ft-lb).


8. Reconnect the water hose


9. Tighten the hose clamps and the job is ready.


HGE being the leader in technological advancement recommends but also supplies each manifold and riser with gaskets made out of material that withstands temperatures above 600oC, non-toxic and without any trace of asbestos.

Alternative types of gaskets :

  1. High Temperature RTV silicone which also can be used with the HGE gaskets especially in cases that the attaching surfaces are not perfectly flat (gaps up to 1/4 in. or 6.3mm can be filled).
    One thing RTV silicone doesnt do well is hold gaskets in place as they are installed. It acts more like a lubricant, making a gasket react like a watermelon seed that squishes out between your fingers.
  2. The shim-type metal gasket which while it acts as a spark plug shield (use these to provide shielding for the plug wires), it has the tendency to create a chemical reaction known as galvanic corrosion. This chemical reaction occurs whenever two different types of metal are joined.
    This combination creates a good environment for electron flow. Unfortunately, this electron flow results in galvanic corrosion of the metal involved, causing one of the metals to be corroded or eaten away by the process.


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