Exhaust flange thread sealant?

[Stu Jackson]

It sounds like the sealant should also be put on the threads, as well as the faces of the gasket, as Ron noted in his earlier referenced "instructions."

[Stu Jackson]

From our other Fleet 1 member who did his recent riser replacement, Duane Quick: 

Yes we both used the same stuff from the same outboard shop and it was the Evinrude gasket sealer and the parts man at the counter in the shop recommended it. 

[Randy and Mary Davison]

Ron,

Posted my reply to the end of the next thread.  Here it is again plus some additional comments:

Ron:

When I take it off, I'll follow your advice exactly.  What I remember from having the riser and flange in hand before is that screwing the riser into the flange hit a solid stop about 4 or 5 turns in.  This was about 90 degrees past where proper riser orientation happened.  I remember others describing the same thing.  I'll figure out what that stop really is.  If it's the threads running out, your suggestion won't work and that may explain why some of us are having recurrent movement - just not enough threads engaged to provide a solid seal.  I'll post what I find when I get it apart.

Randy

Today I spent some time on the Permatex web site plus standing in front of the gasket section of my local NAPA store.  I bought a tube of Permatex Ultra copper which goes to 700F intermittent.  It's the highest temp material I can find in the Permatex line.  I'd really like to know what the temperature actually is at the interface between the riser threads and the flange threads.  A web search shows diesel exhaust temp running from 300F to 1200F but that flange is a bit downstream and the engine itself is a big heatsink.  I'm going to measure flange temperature with my IR thermometer next time we run the engine under full load for a while to try to figure out what we're really dealing with.

Stu mentioned plumbing tape so I also looked for a high temp tape to use for that function.  I bought a package of Muffler bandage to try out.  It's a thin fibrous bandage that's soaked in a sodium silicate solution before application and then sets with high temperature.  I may try this first.  If so, I'll try using it just like plumber's tape, using as many wraps as it takes to cause the joint to tighten up at just about the correct takeoff angle for the riser.  Since the material is "wet" during application, it may help solve the backing off problem that Stu and Ron have discussed.  Hopefully, the tape will mechanically fill the gap between pipe and flange and will provide a matrix for holding the sodium silicate (muffler paste) in position.  I'll report how it works.

Randy

[Randy and Mary Davison]

Well...I thought my riser was stainless from the bend in it but now I'm not sure what's really under the wrapping.  Here is a photo of the whole riser plus one of the flange end unwrapped.  Everything looks solid with no apparent corrosion, pitting, or other problems.  The water injection nipple seems solid as well and makes a "clean" sound when struck with a hammer.

I'm going to goop up the pipe to angle threads and put it back in as have too many projects underway now.  I'm sure it will be good practice to have new one made in the next year or two. 

Any observations or opinions?

Thanks,

Randy

[Ron Hill]

Randy : I'm not too sure who made you riser, but it looks like someone put a galvanized 90 degree elbow then a nipple that attaches to the flange.  The factory ones that I've seen have a bent treaded pipe not an elbow.  It also appears there are still threads on the connecting nipple.

I'd take your riser, clean it up and take it to a plumbing shop and see if they can get that nipple to thread into the riser and elbow further - at least 5-8 turns.  Retap the elbow if necessary as I'd guess that the flange is OK.  If that's a plumbing nipple as it appears, those are probably tapered threads.  I'm not too sure that the flange is a tapered thread, but the elbow probably is ???  Good Luck.   

[Randy and Mary Davison]

Thanks Ron.  I think others probably have this arrangement as well as several have noted the movement and the fact that the threads bottom out 90 degrees around from the properly aligned position.

Since I didn't know there was a junction there, I never used a sealant on those threads.  For the very short term I'm going to goop up the threads with hi temp goo so we can use it for the next two months.  The motion is really quite small and it's on by 4 1/2 turns.  If it starts to wiggle again, I'll pull all the insulation off and have Catalina make me a new stainless one.

Thanks,
Randy