Exhaust manifold Replacement questions

[jakwi]

Hi all,

Well I pulled together the cash to purchase the OEM manifolds, 3 inch spacer and the riser/elbows. I couldn't quite swing the dry joint option, so what I purchased are the E coated wet joint parts. $1036 shipped, which was the most affordable option I found for OEM parts. Thanks to everyone that has answered my previous questions, and helped me figure this out.

Anyway I have a few questions. I've reviewed the manual but it is a little vague on a couple of things.

The torque specs I have are 25lbs for the risers, and 33 lbs for the manifolds

I'm not sure if the 25lb number is valid for 3 inch spacer studs though.
Further I'm a little unsure of the process for installing the studs that secure the risers.

Should I just spin them in finger tight and then torque the nuts on top, or tighten the studs in with vice grips and then torque the nuts?​

How about anti seize? I've read about using anti seize, and also that some recommend marine grease instead. Should it be used on all threaded joints? risers nuts, spacer studs, and Exhaust manifold bolts?

The parts kit I purchased doesn't come with exhaust manifold bolts, I have seen where I can purchase the specified bolts for about $3 each. Is there any reason I can't go to a local nut and bolt place and buy grade 5 bolts? They would certainly be cheaper than $3 each.

Is there a preferred sequence for torquing? How about stepped torques?

Finally what is the best process?
Manifold then riser and elbows, then run to temp, and retorque while hot?, or maybe cold.

How many heat cycles before I can be confident in the torque?

How can you be sure it isn't leaking if the only way to know is to take it apart?

Thanks again for all of the help

 

[jakwi]

So I've been scouring the internet on my questions and have found the following, If anyone has any thoughts, or first hand experience I'd love to hear it. Especially to the "how do you know it's not leaking internally" question.

Studs, According to the article I read regarding head studs, which is not the same thing, but is the only reference I could find to torquing studs; Studs should be finger tight or lightly tightened 8-10 ft lbs, and then the proper torque should be applied to the nut. This sounds reasonable to me, although I was hoping to get some direct experience for marine exhaust. If I don't hear/read anything else though that is what I will be doing.

Antiseize: I found the following by Ricardomarine on another forum. So I'm inclined to use it.

First...... understand that there are two categories for these products.... Auto and Marine.
The Automotive version of Anti-Seize/Never-Seeze may contain aluminum, copper, graphite, etc., suspended in an oily product.
The Automotive version is excellent at/on warm/hot engine related fasteners, and is NOT intended to be used below the water line!
When subjected to water, the aluminum, copper, graphite, etc will cause issues!

The Marine version of Anti-Sieze will not have these components and will be more of a rubber-cement type viscosity (much like the QuickSilver "Perfect Seal"), mainly intended to prevent corrosive water intrusion. This version is intended to be used below the water line.
I would NOT use it at/on warm/hot engine related fasteners.

In asnwer to the thread question...... YES ..... Automotive Anti-Sieze or Never-Seeze is a very good choice for exhaust manifold fasteners.
I would use caution in areas of potenailly wet threads, such as some Manifold-to-Elbow fasteners.
​

Torque sequence: I found this on a separate forum, seems reasonable, but it indicates that I shouldn't use Antiseize. hmmm.

"Bolt torque should be reset after initial startup, while the engine is still warm. Refer to your original manufacturer's engine service manual for specific torque settings.

As a rule of thumb we suggest between 30 - 40 Lb-Ft for 3/8 fasteners threading into cast iron and 20 - 25 Lb-Ft for 3/8 fasteners threading into Aluminum. HOWEVER THE MOST IMPORTANT THING TO REMEMBER WHEN TORQUING MARINE EXHAUST PRODUCTS IS TO PERFORM IN A UNIFORM PATTERN IN ABOUT 2-3 SEPARATE SEQUENCES. 1) 10 LB-FT FOLLOWED BY GOING ON UP TO 15 - 25 LB-FT THEN FOLLOWED BY TAKING THE TORQUE UP TO THE FINAL RATING. THE TORQUE SHOULD THEN BE CHECKED AFTER RUNNING THE ENGINE FOR 30 MINUTES THEN AGAIN AFTER 20 HOURS. Never use anti-seize type products on bolts or studs as this can allow for loosening of the parts."
​

Manifold bolts: I've been searching to see if there is anything special about the OEM bolts, and I haven't been able to find any reference to the bolts other than a debate about using stainless. I'm inclined to use grade 5, or grade 8 though. I would love some input on this.

 

[995jim]

what was the reason for replacing the manifolds? Im not familiar with points of failure
thanks jim

 

[QBhoy]

Hi
to be honest, I’ve done this a few times and each time the manifolds and risers came with new and I stretched/torqued bolts and washers.
If you don’t have them, I strongly recommend you get new bolts to suit..I also used Copperslip grease on the threads and anywhere else I could too. These bolts have a nasty habit of snapping otherwise and especially with the lack of torque or the influence of sea water

 

[jakwi]

995jim: Well when you start to see rust at the joints they say that it is time to pull apart and inspect. That prompted my initial look at my manifolds. Further the common wisdom is that 5-7 years in salt water is about all you will get from the cast iron manifolds and risers. Once I was able to dig in I found that I was at the 7 year mark. I actually was able to get ahold of the shop that did the repower, and he rembered the Previous Owner, and the job. He said that it was a repower due to manifold failure. Once I had mine apart I could see rust spots in the exhaust side of the manifold, on both sides, which is a sure sign of water incursion, so I decided to replace them. I couldn't afford it really, but I can afford a new engine even less. so there you go!

QBhoy: I'm definitely getting new bolts, Most of them came with the kit, except the manifold bolts for some reason. I was just trying to determine if there is any reason I can't get them from a local hardware store rather than buying the branded mercruiser bolts.

Good to know on the copperslip, thanks!

 

[AShipShow]

jakwi, I think you're on the right track, I have nothing to add other than, I can't recall who I learned it from on here, but I started using permatex aviation form-a-gasket as a neverseize/thread sealant and pretty much every bolt on my motor and outdrive and its not failed me yet. It does a great job of sealing threads where needed as well as preventing corrosion.

 

[Lou C]

I have used OMC gasket sealer on the bolts holding in the thermostat housing as per my OMC manual for years. They have never seized in place, even after a bad overheat. The last time I installed new exhaust and also did a top end overhaul with reman heads I used Permatex Aviation for both the cyl head bolts and exhaust manifold bolts. We'll see how well it worked the next time I have to replace the exhaust. The Permatex is rated up to 400* F so it really should be fine in this application.

 

[Bondo]

I can't recall who I learned it from on here, but I started using permatex aviation form-a-gasket as a neverseize/thread sealant and pretty much every bolt on my motor and outdrive and its not failed me yet. It does a great job of sealing threads where needed as well as preventing corrosion.

Ayuh,..... It took awhile, but DonS convinced me to toss the never seize, 'n switch to perfect seal/ permatex #3,.......

Never been a problem,..... Wish I'd switched decades ago,.....

 

[jakwi]

I know this is a super old post, but I've been meaning to update it with some info for future reference, in case anyone else ever has these questions.

I'm not sure if the 25lb number is valid for 3 inch spacer studs though.Is there a preferred sequence for torquing? How about stepped torques?

I don't know if it's valid, but that's what I've used, and it's been more than a year now and no issues. I torqued in steps. first 10lbs, then 15, then 20, etc using a cross pattern. I then ran it for an 20 min and re torqued. Then retorqued after another hour run, then again after maybe 8 hours. I haven't re torqued since. Actually I'm wondering if I should re torque now that it has been a year.

Further I'm a little unsure of the process for installing the studs that secure the risers.

Should I just spin them in finger tight and then torque the nuts on top, or tighten the studs in with vice grips and then torque the nuts?​

There is no finger tight on these. After about one rotation they are finger tight, but if you go with that you will crack the manifold because it isn't fully seated. I had to use vicegrips to insert the studs. I suppose you could use the double nut method. I threaded them in until the threads were all fully seated in the manifold. No further, no less.

How about anti seize? I've read about using anti seize, and also that some recommend marine grease instead. Should it be used on all threaded joints? risers nuts, spacer studs, and Exhaust manifold bolts?

I used anti sieze on the exhaust manifold bolts, but not the riser studs as the riser studs came with loctite on them.

The parts kit I purchased doesn't come with exhaust manifold bolts, I have seen where I can purchase the specified bolts for about $3 each. Is there any reason I can't go to a local nut and bolt place and buy grade 5 bolts? They would certainly be cheaper than $3 each.

I went to the local nut and bolt place. Way cheaper, no discernible difference.


Overall I found that this was a lot easier than I had anticipated. The biggest issue was expense, but what do you do.

I also want to mention Saltaway. I did a lot of reading on this, as best as I can tell it is vinegar and a surfectant. I decided to rinse with Vinegar and Dawn dishsoap, which is also a surfectant.

No way to know if this will be helpful or not, but I figured at $3 a gallon why not. it's cheap and I can figure out if it is working after the fact. If it does great, if it doesn't oh well I didn't waste that much money.

I purchased a fertilizer injector that connects in line to the hose. Chapin, 4701, 24 OZ Fertilizer Injector. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

My process is to add about 2 or 3 oz of dawn into the reservoir, and then I add distilled vinegar on top of that. I put this inline to my hose and run the engine on muffs until it is up to temp, and soapy water is ejecting from the ports. Then I leave it. I do this every time I run in salt or brackish water, after I get back to the house.

What ever is remaining in the reservoir is used for boat cleaning. The vinegar really helps remove the salt from the boat.

Time will tell whether it makes any difference. Anyway I hope this helps someone.

 

[AShipShow]

Thanks for the followup! Glad to see its all working out.

 

[Davetowz]

Thanks for the followup. I often wonder about the log term outcomes of many posts.

 

[jakwi]

I know this is a super old post, but I've been meaning to update it with some info for future reference, in case anyone else ever has these questions.

...

I also want to mention Saltaway. I did a lot of reading on this, as best as I can tell it is vinegar and a surfectant. I decided to rinse with Vinegar and Dawn dishsoap, which is also a surfectant.

No way to know if this will be helpful or not, but I figured at $3 a gallon why not. it's cheap and I can figure out if it is working after the fact. If it does great, if it doesn't oh well I didn't waste that much money.

I purchased a fertilizer injector that connects in line to the hose. Chapin, 4701, 24 OZ Fertilizer Injector. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

My process is to add about 2 or 3 oz of dawn into the reservoir, and then I add distilled vinegar on top of that. I put this inline to my hose and run the engine on muffs until it is up to temp, and soapy water is ejecting from the ports. Then I leave it. I do this every time I run in salt or brackish water, after I get back to the house.

What ever is remaining in the reservoir is used for boat cleaning. The vinegar really helps remove the salt from the boat.

Time will tell whether it makes any difference. Anyway I hope this helps someone.

So here is the four year follow-up on the "saltaway concoction, These manifolds were installed in March of 2019. I've been very diligent about rinsing with my homemade version of saltaway as described in my previous comment. My activity is about 90% Brackish with the rest in Fresh water. Add in one week in the keys over the last four years. At home I always rinse with my mixture at the end of the day when back home. We tend to boat weekly for about half of the year There was one time when we arrived too late and I rinsed it the following morning. While in the keys the boat was in the water for the entire week, on the water on both the Atlantic and gulf side. I have a inline connection to rinse with fresh water, which I did every day once back on the dock, but I wasn't able to use the vinegar soap mixture, so for that week only I rinsed with fresh water only.
Port side seems to have held up better, than the starboard side, but I really have no qualms about continuing to used these manifolds. I have to pull the motor this year as my oil pan has rusted out, so that is why I disassembled.

My plan is to retorque and carry on for at least two more years then check again.
Thoughts, comments? I don't have a basis for comparison to a consistent fresh water rinse, but Maybe you guys can tell me if this looks better or worse than expected. .

 

[dubs283]

Not bad for four years, rinsing with freshwater/solution is key for salt/brackish water use

Would be more interested in seeing the water and exhaust passages at the seam between the manifold and riser, also is good to inspect for water intrusion in the manifold exhaust passages

 

[jakwi]

Agreed, but I don't want to disassemble them now. When I do finally take them apart I will update this thread.

I think the homemade saltaway was worthwhile.

I might see if I can borrow a boroscope though, that would allow me a look.