Exhaust Manifold Threads Stripped

[ccriders]

I had someone work on my exhaust system and now find that the bottom threads on the exhaust manifold are partly stripped out. It seems that previously a different length bolt (shorter) was used to secure the riser flange to the manifold and as a result the outermost 1/4 inch of threads were pulled out with the bolt, which leaves about 1/4 inch of threads still there.
Is this amount (1/4 inch) adequate to reattach the riser and flange to the manifold? If not, what are my courses of action?

Second issue: The riser/dry section of the exhaust is 1 & 5/8 inch OD pipe (I believe bronze) and the pipe that the hose to the muffler fits on is 1 & 5/8 inch OD with threads (not hose barb). The hose is 1 & 5/8 inch ID. The input flange to the muffler is 1 & 1/2 outside diameter. What started me on this job was a leak in this hose where it attaches to the muffler. When I took the muffler out I found that the plywood platform it sits on to be completely dissentegrated from rot and that the inside membrane of the hose was completely distorted. So this has been going on for some time. I now have a 1 & 1/2 inch hose barb to 1 & 5/8 inch pipe fitting. But now I'm thinking that this reduces the ID of the system to less that 1 & 1/2 inches and that it might cause more back pressure on the system. So, what is the ideal ID of an exhaust system for an Atomic Four?

I will really appreciate your insight on these two questions.
John

[sastanley]

Issue #1 - I would try a thread chaser first. The function a thread chaser performs is similar to a tap, but it is a different tool...its job is to clean up existing threads, like what you are dealing with. It's cheaper than a new manifold, & probably easier than drilling & tapping a larger hole there, of which there may be additional implications.
I own this set...it has saved my butt a few times related to various projects..
thread chaser set - Sears

Issue #2 - Most of us are running 1 5/8" ID exhaust hose, if for no other reason than that was the OEM choice. The correct size exhaust is always up for debate...so you may get a few different answers as to what is 'ideal'.

Snapping a few pictures of your situation always helps. It makes it lots easier to make suggestions too and see what you are dealing with. Things like exhaust systems are pretty varied, as the boat's design and engine placement often dictates some things.

P.S.> Welcome to the forum. I think you'll find that with the knowldege available here, that will be the last time you'll pay someone else to work on your engine...the results you are dealing with speak for themselves.

[Dave Neptune]

John, welcome to the MMI Afourian Forum. John what Shawn said is very good. That you stated the hose was bad, I'm guessing that the inside had broken down and was leaking. That means the hose was old and if it were mine I would take a good look at the water injection area before I did anything in the way of repair. My boat has an extremely long exhaust run as my engine is in the middle of the boat and the exhaust is on the transom. I have over 25" of the 1 5/8 hose attached to the 1 1/2 std pipe and I have very good performance overall. The engine achieves full rpm's with the Indigo prop, a good baseline around here.

Fair winds and welcome _/) _/)
Dave Neptune

[ILikeRust]

Originally Posted by ccriders

So, what is the ideal ID of an exhaust system for an Atomic Four?

Uh-oh, now you've done it!

Paging Dr. Hanley; Paging Dr. Hanley...

[ndutton]

What type/construction/condition is the muffler? Where I'm leading is new quality mufflers don't cost that much and you would also be able to get one with fittings that match everything else. Mismatches are invitations to leaks.

[sastanley]

Ah....here we go. some more good reading on exhaust sizes.

http://www.moyermarine.com/forums/showthread.php?t=4430

[hanleyclifford]

Thanks to Shawn for referencing the "size" thread. I think we sort of concluded that 1 1/2" to 2" is the ideal hot section size, but I would recommend opening the flange up to 1 1/2" so it does not become the bottleneck. As Neil pointed out, the larger the tail hose section, the more water that must be batched. As always, we are looking for the "sweet spot". I find the 2" hose to be satisfactory.

[ccriders]

Thank yous to everyone for your advice. I've been fiddling around trying to up load photos of my exhaust system but, alas, I've not been successful.
Nonetheless, I decided that apipe to hose nipple would not reduce the overall ID of the exhaust system as there is an elbow that goes inside thread to outside thread that has the same ID as the pipe to hose nipple. So I proceeded with taking off the pipe to pipe connector and what a job that was. Took a much larger pipe wrench and cheater bar than my injured arm and hand could handle so I hired it out. When the connector finally came out, it left its threads in the elbow to which it is connected. The PO had a new exhaust system installed sometime before I bought the boat and used 304 stainless steel with teflon tape on all the threads. So maybe teflon tape is not good enough for exhaust systems. Had the threads chased and cleaned and the stack is now installed on the boat.
I purchased some gasket material - metal with paper on one side - and made a gasket (PRO_RAMIC is the name of the material).
After carefully measuring the manifold I discovered that there are about 7/16 inch of useable threads left and that if I used a longer bolt that was in there that I could get a solid fit. I cannot find torque specs for these bolts, but since the is 30 ftpnds then I shouldn't be more than that.
So two questions left:
What torque?
And should I use thread locker or some other anti seize compound?
Thanks again for your help.
John

[roadnsky]

John-

There really isn't a torque spec for those bolts (from an old post comment I remember from Don)
30 ftp's would be fine (and safe) assuming a good quality bolt.
No need for a "locktite" thread compound but many of us like to coat the threads with Permatex to seal against any possibility of leaks.

AND, welcome to the forum crew too!

Edit: Found Don's old post http://www.moyermarine.com/forums/sh...e+bolts+torque
"There is no published torque specification on the manifold exhaust flange bolts."

[sastanley]

John,

I've posted this screenshot quite a few times, hopefully it will help you too.

[Mo]

Shawn,
Since Jan 10th I'm on my 3rd new laptop...yep 3 of them. This one is a HP and I had toshibas for years...got two that went south in no time. Anyway, I have to use "paint" to resize pics on this. So the question is....what size do you resize them to .... I put in 800 pixels on the top row and it auto enter 600 pixels on the bottom row in the resize box.
Thanks in advance.

[ILikeRust]

A good general size for pics is 640 x 480.

I have a free Photobucket account, which includes photo editing capabilities. It's very easy to use.

[edwardc]

I usually do then 800 pixels wide and leave "preserve aspect ratio" checked, and take whatever height comes out. This way the pictures don't get distorted (squashed or stretched).

[sastanley]

what ed said..the key is to keep the aspect ratio so the image doesn't get distorted.

As to what size I set them, it depends on what I am doing...When I am e-mailing them to someone I usually make them pretty small..prolly 640 x 480 to keep the file size down, even though these days most everyone has pretty fast internet. For this forum, most of 'em are probably 800 x 600.

The XP "picture resizer" utility has three options, small (640 x 480), medium (800 x 600) and large (1024x768), and obviously that utility was built before widescreen ratios became the norm. That works OK for me, because all my cameras are also still set up at a 4:3 ratio by default..none of the 'boat' pics are ever taken at a widescreen aspect ratio.

If you get some time, try paint.NET. it is free, and leaps and bounds better than MS paint. My latest laptop is a Windows 7 machine, so my beloved XP utility won't run on it, but I also have paint.NET installed on all my XP machines too.

And if you all go and get photobucket accounts like Bill, I'll be screwed because PB is blocked at work..Bill's posts are always much more interesting at home, since none of the captions from his photos make any sense when I view his posts from work..