Exhaust port/flange- gasket or no gasket?

Hi Folks

Do you use a gasket between the exhaust exit flange and the manifold header that bolts on to it?

Here is the reason for my question:

The first time I ran my previous gas (Zen) boat I used the supplied stock gasket which appeared to be made of a composite material. It blew out after about 15 minutes running despite the connecting bolts being very tight.

I took advice from more experienced people than I and was told to ditch the gasket and simply tightly bolt the header straight on to the exhaust flange. The reasoning given being that the gasket is one extra (unnecessary) component that can fail.

Since then I have operated without gaskets. My current Lynx (with stock Zen260 PUM) has behaved fine without the gasket. After a day’s running there is a little oil seepage between the joint but just a smear underneath easily cleaned away. I might be tempted to finely hone the mating surfaces to all but eliminate that little bit of seepage.

So is there really a need for a gasket or does it cause more problems than it might solve?

Your comments and advice will be much appreciated.

Regards
Craig

For years when the exhaust manifolds had water circulating around the o-rings running manifold to cylinder as metal on metal with a sealant was the norm.
*Now with the more common "No Leak" style manifolds water no longer cools the rings by direct contact with water but relies upon the flange to be cooled enough to prevent rings from getting damaged.
Personally have found USING the composition exhaust gasket has helped the flange too lose it's heat better and o-ring life is better now. ( Without a gasket the cylinders heat is transferred to flange and it just does not get cooled down much having o-rings burn up faster. )


JMO ...

Thanks for your prompt response Scott.

The concern I have with a composite gasket (preventing heat energy transfer from the exhaust port to the water cooled flange) is that the exhaust port will get potentially very hot.

The thought I have is that if the flange (metal to metal) is sufficiently well engineered to incorporate the O rings (seated properly) with minimal contact exposure to the hot exhaust gasses, the water cooling jacket should help spread the heat giving long lasting O rings and more uniform cooling to the exhaust exit side of the cylinder.

Scott, I am interested in these “no leak” style manifolds. Would you or any members be able to include a photo within this thread so that I and see what they are about?

Cheers

Craig

I'm the same as Scott I use a factory gasket (some after market last 30 secs) works for me

no leak below

www.gizmomotors.com/index.php?...emart&Itemid=56

Thank you CHR.

I appreciate the link that you provided.

Regards
Craig

Canadian Hot Rod RC Boats wrote:

I'm the same as Scott I use a factory gasket (some after market last 30 secs) works for me

no leak below

www.gizmomotors.com/index.php?...emart&Itemid=56

That general style ( No leak ) are named so because NO water can get into pipe/engine when an o-ring fails. Only leak is that of exhaust gas's which effects nothing but noise and maybe power a tad.

Having an o-ring failure on water circulation around ring type flanges are real power killer when they lose a ring because water is allowed into pipe and engine while running :S

Thanks Scott for your further sage advice.

Even though I have yet to have an O ring failure on my current gas boat (ring type flange), when I do eventually get one I will consider the “No Leak” alternative.

Thanks again for your advice and comments.

Craig

Craig

Prestwich Model Centre sells the no leak manifold in CNC Aluminium. As you know, I use this on my Sikk engine.

Brigadair

Brigadair wrote:

Craig

Prestwich Model Centre sells the no leak manifold in CNC Aluminium. As you know, I use this on my Sikk engine.

Brigadair

CS 61 from Dave

www.prestwich.ndirect.co.uk/gaspipes.htm

no actual gasket here... and no o-ring problems. I use a Anaerobic gasket maker.