Although I can't offer the explanation you seek, I do have a question for you which may or may not be pertinent. Does the exhaust riser connect to the muffler via a piece of rigid black exhaust hose, or does it connect via a hump hose?

From your photo, it looks like the expanded metal cage has some serious corrosion. IF the cage is carbon steel this would make sense. Even "Stainless" steel will rust, especially when in contact with carbon steel.
Given the boat was laid up for a couple of years in a damp (near the water) environment, condensation will occur (especially in salt air). Without regular running to heat and dry the insulation, the condensation will build up soaking the insualtion, the rust will really set in and "Bob's your uncle" as Aussies would say.
Personally, I'd lose the cage and get some good modern insulation wrap for the pipe.

Chooch, do you have a recommendation for a 'modern' technique to wrap the riser? How would you do it if it were your boat?

Hey guys, I went through what your discussion is about last year. Being that I am in fresh water and had the red dust as well, Like Cooch says. It is the expanded metal that is providing the red dust. I Thought I had a crack in the exhaust riser cuz of the dust. So I pulled it out and magna fluxed it myself and found no cracks. But the cage was getting bad.

So I had some butter cup screen which is for putting fake rock on a home. It is pretty much the same stuff on it. So I went with that and then used this heat wrap and bought 15ft x 2 inch. Worked like a top. [URL="http://www.alamomotorsports.com/thermotec/originalexhaust.html"]http://www.alamomotorsports.com/thermotec/originalexhaust.html[/URL]

Randy

Sorry for the late response to Larry’s question of 5 DEC. Just finished an annual curriculum review for a dozen Navy courses.:eek:

Fortunately(?) Catalina provide a very nice aluminum-shielded exhaust wrap with the replacement stainless exhaust pipe with cooling nipple I had to buy last year.
However, if I was replacing Tara’s exhaust installation today, I’d use a product like HP Armor-Marine exhaust heat shield [url]http://www.heatshieldproducts.com/m_hp_armor.php[/url] for ease of installation and performance.
Another alternative would be to use a more conventional wrap [url]http://www.heatshieldproducts.com/m_exhaust_wrap.php[/url] and outer-wrap. This is what we had on Tara before the old, carbon-steel exhaust pipe rusted out and changed our white bilges to a sooty charcoal color.

Either one will do the job, but I would prefer the heat shield if I had my ‘druthers.

Ok. Here is some more good info for the 36 Site, Not being able to be 100% sure of the red dust a few of us have noticed on and around the rear of the motor and transmission. After a message to Bud Street our Tech Editor. He helped me find the past posting for a question I had to him. I found the posting and read it again but could not get a good answer from what I was reading.

So, red dust here I come. My thought process was two fold, remove the stater first as it was was the easiest thing to remove in search of the red dust. Which by the way the part number on the starter is 15504-63011.

Starter off and yes it pointed me to remove the bell housing and transmission. Looking at the easiest way out. I decided to take the bell housing and transmission out in one unit. I had to polish the prop shaft to slide the ring up for the drip less coupling. Taking care of the o-rings inside the donut, Grease helps. No trouble,worked well. Next I separated the shaft coupling by removing the 4 bolts and nuts and slid the shaft out of the boat about 8 inches. This then gave me the needed room to get the bell housing and transmission out in one piece.

I took and removed the top nuts from the rear motor mounts. Then took and blocked the rear of the motor up about 1/2 inch with wood just under the back edge of the oil pan. Not in the middle of the pan but on the back edge. As this is the stronger point of the oil pan. Then I removed the 4 lag screws that held the rear motor mounts in place. Next was to remove the bolts that held the bell housing onto the back side of the motor. Once all removed there are 2 pusher holes that you take 2 of the same bolts that hold it on and use them to pushes the bell housing off of one alinement pin. Once off the pin just pull the whole housing and transmission out the back as it will come off the damper plate that is bolted to the fly wheel. The whole unit weights about 20/25 lbs I am guessing.

I was not sure if the damper plate had a fiber disk in it or not and it does not. Where the dust comes from is the middle plate that the 6 springs ride on. There are 3 sets of 2 springs each, each set of springs have a different tension rating just by looking at the wire size of the spring and number of coils. These are what takes the shock load from putting your boat in forward or reverse. Over time they just start to wear into the middle plate. I had only a small amount of rattle at idle but it was the dust I did not like, It is not normal. After looking at the plate It could have went on one heck of a lot longer if you like to clean the dust up. Not me as it was getting into other components that would fail just with the dust, We have 2354 hours on the diesel for a reference for you all.