New hot section: Do I need to remove exhaust flange?

[ernst]

This may be too late to help in this case, but my technique for removing the pipe from the exhaust flange is as follows: a) cut the pipe off about 1/8" from the flange, b) using a sawz-all, put two cuts on the ID of the remaining pipe about 1/4" apart, c) using a screwdriver and a hammer, remove the piece of pipe between the cuts, and d) collapse and remove the remaining piece of pipe.

I may do this on the old flange, just for kicks... Thanks.

[ernst]

This is a very typical failure in the hot section. The nipple is exposed to some of the hottest gases, and the bottom of the thread grooves in the nipple are the thinnest point of the whole system. And its under the worst stress from the weight of the system.

I've seen three hot section failures on other boats, and they all played out like this. It's one of the reasons I went with stainless pipe when I rebuilt my hot section. Hopefully it will hold up better.

Where can you buy stainless components, like nipples?

[67c&ccorv]

Where can you buy stainless components, like nipples?

I have been using these guys;

https://www.buyfittingsonline.com

They take Paypal - go for the 316 S/S - it isn't much more than 304 S/S but is much more suitable for marine use.

[ernst]

I have been using these guys;

https://www.buyfittingsonline.com

They take Paypal - go for the 316 S/S - it isn't much more than 304 S/S but is much more suitable for marine use.

Thank you for the link!

Do you have any experience about the longevity of S/S in this application?

[hanleyclifford]

If you decide to go with SS components be sure not to wrap them. They do not like the anerobic environment.

[ernst]

If you decide to go with SS components be sure not to wrap them. They do not like the anerobic environment.

Well, that does not seem practical on my boat. I would be concerned about starting a fire and certainly about melting hoses, cable insulation etc.

Also, the corrosion seems always to start from the inside. Isn't that very anaerobic? OTOH, I found the ABYC rules for exhaust (http://dms.ntsb.gov/pubdms/search/do...num=DCA97MM012.) and they, indeed, list stainless (316L) together with black iron.

[hanleyclifford]

In most cases exhaust hot sections do not corrode from the inside where a coating of carbon usually offers protection. The corrosion usually is on the outside where moisture collects between the pipe and the wrap. The stainless pipe would only offer an advantage if it can be left unwrapped. IMO, SS is not worth the extra money. A black iron rig should be good for 7 or 8 years easily, then just replace the whole thing again.

[ernst]

In most cases exhaust hot sections do not corrode from the inside where a coating of carbon usually offers protection. The corrosion usually is on the outside where moisture collects between the pipe and the wrap. The stainless pipe would only offer an advantage if it can be left unwrapped. IMO, SS is not worth the extra money. A black iron rig should be good for 7 or 8 years easily, then just replace the whole thing again.

I see, that's interesting. I had thought it was from inside out but I am always willing to learn.

Black iron is certainly MUCH more cost effective! And indeed mine held up for 8 years.

[hanleyclifford]

Eight years and still strong. Paint and wrap.http://www.moyermarine.com/forums/pi...&pictureid=701

[ernst]

Eight years and still strong. Paint and wrap.http://www.moyermarine.com/forums/pi...&pictureid=701

paint with what?

[sastanley]

here ya go hanley..

Wrap the [ img ] tag around that and it should show right up in the thread!

(Hit the quote button on my post to see how I did it.)

This is also the same trick you can use to re-post photos without uploading them multiple times on the forum..once it is uploaded, it lives here..use your "User CP" to find all attachments you've previously uploaded and simply wrap the URL of the picture's location with the same [ img ] tag (with no spaces).

[hanleyclifford]

paint with what?

I use automotive header paint. Etch first with muriatic acid (work carefully).

[ernst]

I use automotive header paint. Etch first with muriatic acid (work carefully).

Hm. I have added a can of High heat coating from MMI's exhaust section to my order. I hope that will have a similar effect.

[ernst]

A bad purchase, and a new improved material

Hm. I have added a can of High heat coating from MMI's exhaust section to my order. I hope that will have a similar effect.

Just got my package from MMI, as usual superfast (ordered Sunday night). Looks good, but it turns out the spray-on heat coating is really for the wrapper, not for the pipes (only good up to 1200F). I will re-use my fiberglass exhaust wrap, not the MMI wrapper so I guess I bought this for nothing. Anyone wants it?

"In other news," a friend suggested to use Schedule 80 instead of Schedule 40 pipes, because of the thicker walls. That makes a lot of sense, I will do that.

[sastanley]

Whoa...ernst, I am confused.

Why not wrap the pipe in the new Moyer wrap, and then spray the wrap with the spray? I think that is how it goes, unless I do not understand how it works.

What is the difference between the wrap you have and the stuff you got from Moyer...??