sealing exhaust steel surface with Permatex Orange gasket maker High heat version

Discussion in 'Powerboats' started by sdowney717, May 24, 2015.

  1. sdowney717
    Joined: Nov 2010
    Posts: 829
    Likes: 30, Points: 28, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    I have discovered that this stuff here.
    http://www.permatex.com/products-2/...sor-safe-high-temp-rtv-silicone-gasket-detail
    [​IMG]

    Will not burn off the surface of an exhaust manifold.

    I first used this instead of an exhaust gasket between head and manifold on my Palmer IHC 392 engine. The mating surface of the manifold had some rusted defects and the standard gasket could not seal it. Since then I resurfaced the manifold on an engine rebuild. But it worked filling a 1/16 inch gap.

    Second was on the Onan 6500 MCCK. The exhaust gasket had failed. I used this instead AND I coated on the lower flange of the exhaust manifold where it always burnt off any paint and it would rust there. Now after couple years, this Permatex orange is intact and NO rust appearing on the exhaust manifold.

    Third is recently on the starboard engine, the part that joins water cooled exhaust manifold to water cooled riser rusted through. The part is at least 30 years old, maybe even to 1970 and made of cast iron. This short part has no water cooling and gets very hot. I had a machine shop fabricate a new part from steel. I thought why not coat with permatex orange, and I had no gaskets to use.

    So I coated entire part with Permatex orange, smeared on the inside and outside. and used it for a gasket. Result was perfect, ran all day, no leaks.

    Came back to slip and checked it. Perfect, no discolor, no burning off, still well attached to the steel. My thinking is it will seal the steel and it wont rust.

    I see Permatex has one with slightly higher heat than this one. So if you want to keep rust away on exhaust manifold surfaces, try it.
     
  2. sdowney717
    Joined: Nov 2010
    Posts: 829
    Likes: 30, Points: 28, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    I took a picture, and notice it is holding up under the heat of the exhaust without burning off. No paint could do this I think.
    This part joins the FWC exhaust manifold on left to the FWC riser on the right. Someday I will take it apart and see how it is holding up on the inside surface exposed to the exhaust. there are two clamps and you can swivel this riser, rotate it to fit. The old gasket when I took this apart to replace this 1970 part, it had rusted out with a hole badly, gasket broke apart, so it is just sealed with the orange permatex gasket maker and holding up perfectly.

    [​IMG]


    Back in 1999, I bought four new risers for $250 each. As originally designed, they were raw water cooled, water in at the bottom, comes out a 3/8 discharge hole on the inside. I decided to make them FWC. I popped out the brass plug on top and brazed on a 3/4 elbow. I brazed a bolt into the 3/8 inner water discharge hole. Then I brazed a 3 inch diameter 6 inch long bronze pipe nipple onto the hose end of the riser. The nipple was a 12 inch pipe which I sliced in half. I think it was 12 inches long, might have been 10 inches long. It needs to be as long as it should be too work. As you can see, it does not get hot enough at the braze joint to burn off any paint.

    I drilled a hole at an angle into the new bronze extension and silver brazed the SS to the bronze nipple.
    This shows how it looks.
    [​IMG]
    It has been working fine since 1999. I recently took the hose and riser off and it looks real good, just some surface rust on the riser on the inside exhaust passage.
    At the time I had wondered if the heat exchanger could handle including the risers in the FWC circuit, and found out they can, the engine runs at the same temperature as before. Not all risers could be so easily modified this way, some have many discharge holes or slots in a ring, you would have to braze them all up. Some risers are designed to be in the FWC cooling circuit, they have an expendable bolt on cast iron tail piece. I think my idea is better, there is no corrosion of the bronze pipe extension.

    The red hose is the raw water hose, the black hose to the left on the brazed on elbow is the FWC hose. There were no threads cut in the riser there, it only had the brass core plug, or I could have simply screwed on a pipe nipple. And I had no large pipe tap.
     
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