Exhaust Manifold Replacement - Marine Torq Stainless Steel

[justgary]

A short video at 1600 RPM from inside the boat.

 

[justgary]

Imgur is apparently mad at me right now for something.  I have a few more photos to upload, but I'll describe the rest of the install for now.

When I took the doghouse off and removed the rear floor hatch, I figured out that I could use the existing exhaust hoses by just lifting the mufflers off the floor a bit.  I got a good two inches of pipe into each one, which is close to what the original manifolds had.  If I see any problems in the future, I can still cut some "new" hose and change them out fairly easily.

I had been wondering when I would find the time to change the transmission oil, so I did that while I had the hood off.  I forgot to grease the rudder.  I can lift the floor hatch and do that, though.

The highest temperature I saw with the IR temp gun was about 422*F on the siamese pipes near the water jacket of the manifolds.  Temperature readings with an IR gun should really only be made on a non-reflective black surface since they are calibrated for a specific emissivity.  As a friend that works with IR imagery at the Air Force Research Laboratory told me, "just put a piece of black electrical tape on it and it will read close enough."  Well, I didn't have my tape with me, so you don't get good measurements of the manifolds.  I'll try to remember next time I have the boat out. 

The manifolds were only warm, as was the heat exchanger while the engine was 155*F-160*F.  I have very good pressure and flow from my garden hose, so the exchanger was not working very hard.  The only hot spot I found (besides the uncooled sections of pipe) were right at the top of the manifolds where the hot exhaust from the header pipes hits and takes the sharp turn to the outlet pipe.  The port one was hotter than the starboard one, but I don't know if that is a water flow thing or not.  It is possible that the exhaust tube on that side is a little closer to the water jacket.  I could hold my hand on the lowest part of the water jacket, so I think everything is good to go.

OK, Imgur is back now....

Here is what I mean about emissivity.  The reading close to the hot spot is way too cold, but the black hose shows the correct temperature (according to my calibrated hand).

 

[justgary]

I don't see any reason why you all shouldn't grab a set of these for your boats.  Any objections to actually opening the group buy?

[maxfir]

They look absolutely amazing so far, appreciate you doing so much validation for the group buy. My only questions really come down to version details and maintenance.
 

1. Is there a mapping of their models (i.e. HT1) to engines?

2. Are we able to buy additional anodes online?
 

I have a 1994 Malibu Echelon with original 350 Magnum EFI TBI. 

[justgary]

40 minutes ago, maxfir said:

They look absolutely amazing so far, appreciate you doing so much validation for the group buy. My only questions really come down to version details and maintenance.
 

1. Is there a mapping of their models (i.e. HT1) to engines?

2. Are we able to buy additional anodes online?
 

I have a 1994 Malibu Echelon with original 350 Magnum EFI TBI. 

Honestly, I think that their mapping of parts to engines is one of the things that is holding them back.  I have seen their list, and you really can't tell what to order from the descriptions.  My understanding is that they are hiring a retired employee to make a datasheet for them since he has the most corporate knowledge about the development of most of their models.  I know that it is a priority for the new dealer here to be able to sell manifolds in a more direct way.  Unfortunately, the order form has to go to Australia for them to decide the model you need.  In reality, that's kind of good since it is on them if it doesn't fit right.  Given the build to order nature, a few days to let somebody else figure it out didn't bother me at all.

As for the anodes, three sets should come with each manifold order.  Extra anodes will be available from the dealer here by the time you would need them.

[justgary]

I just remembered to retorque the manifold bolts after my engine run the other day.  All of them seemed tight still, so that is good.  I'll check them again the next time I get the engine hot.

The group buy is on.  If you are even wondering about a set, send an email and get the form, fill it out, and return it.

[justgary]

When @Bozboat took a boat ride with us on New Year's Eve he asked if I had insulated the hood.  When I reminded him that I had just changed the manifolds, he peeked under the hood and saw the new manifolds for the first time.

He has never heard my boat before, so it is not a direct comparison for him, but I personally think that the engine is quieter now from inside the boat.

[maxfir]

Appreciate the update @justgary. Please keep them coming with any new info. I started the process shortly after the group buy started and locked my spot. Looks like I need a set of their HT-1 manifolds. They have 1 set available built but I've asked for a set with O2 ports in them to support any future EFI upgrades (earlier Holley Sniper comment has me interested if my OEM TBI ever fails). Will put stainless plugs in the ports to start.

 

Installation question, did you use the Permatex Ultra Copper 1) in place of or 2) in addition to the supplied gasket? 

[Bozboat]

1 hour ago, justgary said:

When @Bozboat took a boat ride with us on New Year's Eve he asked if I had insulated the hood.  When I reminded him that I had just changed the manifolds, he peeked under the hood and saw the new manifolds for the first time.

He has never heard my boat before, so it is not a direct comparison for him, but I personally think that the engine is quieter now from inside the boat.

They are some serious bling but more impressive is they are cool to the touch and somehow get rid of engine noise.  (I have the same engine in the same direct drive configuration) 

[Woodski]

Thanks for the updates, sounds like the manifolds are working well.  @justgary As for the temperature drop and the accompanying noise reduction, do you think the source could be more water in the jacket?  Another possibility would be less restriction allowing an increase in water flow.  I am going to assume you might not have done an oil pan / oil filter temp check after a typical ski set to see if any different.  As a comparison to your data, after a hard ski run my aluminum exhaust manifolds read ~110 degrees after I come to a stop so that allows a bit of cooling from the idle, any cast iron ones are significantly higher, more in the 180+ degree and too hot to touch zone.

Adding an O2 sensor bung makes a lot of sense, I would imagine a fair number of customers would be interested in doing a DIY FI system along with this addition.  @maxfir where are you having them added (orientation relative to pipe).

[justgary]

2 hours ago, maxfir said:

Appreciate the update @justgary. Please keep them coming with any new info. I started the process shortly after the group buy started and locked my spot. Looks like I need a set of their HT-1 manifolds. They have 1 set available built but I've asked for a set with O2 ports in them to support any future EFI upgrades (earlier Holley Sniper comment has me interested if my OEM TBI ever fails). Will put stainless plugs in the ports to start.

 

Installation question, did you use the Permatex Ultra Copper 1) in place of or 2) in addition to the supplied gasket? 

I used just the ultra copper and hung the gaskets on the wall.

[justgary]

@Woodski- My old iron manifolds ran consistently at about 160*F.  I have not checked these after any extended ski speed run, but @Bozboat watched me put my hand flat on the manifold hump as we idled around the dolphins near the Destin bridge.

I do suspect that it is from improved water volume and flow in the jackets.  That should have a good damping effect on the exhaust noise as well.

[maxfir]

@Woodski, they provided a picture of their HT-41 with O2 ports for an LS engine. I was planning on placing my O2 ports similarly. I've linked the photos below for reference. Do you have a recommendation for O2 port location?

 

HT-41 (LS engine manifold) O2 port example: https://1drv.ms/u/s!AkfZ8_WsCz-uukJOwX3NWqchM1YZ

HT-1 (blue dot marks their recommendation of location): https://1drv.ms/u/s!AkfZ8_WsCz-uukP8Jymg0r4J4-gk

 

My thinking is does not matter if electronics control box impedes the location, as if I convert, I will likely remove the control box entirely or place sensor in the other manifold. 

[justgary]

30 minutes ago, maxfir said:

or place sensor in the other manifold. 

Doesn't the ECM kit want a sensor in each manifold?

[justgary]

The picture of the HT-41 set looks like the O2 ports are just barely at the top of the header pipes if they are built like mine (which I suspect they are).  I would probably want to put them just after the hump, basically at the beginning of the straight outlet pipe so the gasses from all cylinders on that side can mix and get sampled.

I guess that bracket shown holds your control box?  How much space does it take up along the manifold?

[justgary]

I moved them to Imjur for you so they are easier to see.

HT-41 with O2 Sensors:

HT-1 with bracket:

[maxfir]

Thank you for transferring the photo links @justgary! Based on your comment:

1 hour ago, justgary said:

I would probably want to put them just after the hump, basically at the beginning of the straight outlet pipe

I should go with the recommended blue dot location. Or are you recommending further back on the pipe outlet?

 

1 hour ago, justgary said:

I guess that bracket shown holds your control box?  How much space does it take up along the manifold?

 

Yes, bracket holds the control box. Here's an older top-down view of my engine: https://1drv.ms/u/s!AkfZ8_WsCz-uukRVRDaVB7XZtkF7?e=1XQSRf. Control box is relatively long. However again I believe this would be removed should I convert the engine to the Holey EFI.

[maxfir]

1 hour ago, justgary said:

Doesn't the ECM kit want a sensor in each manifold?

Looking at the Holey Sniper Kit, I only see 1 sensor, however I have not researched much: https://www.holley.com/products/marine_and_powersports/marine/sniper_efi_marine/sniper_efi_4150_marine/parts/550-510

[maxfir]

Update: finalized my order today. Took a few weeks to lock in the details due to the holidays and I needed dimensions from the boat that was tucked away in storage for the winter. They had a set in stock available, but since I wanted the O2 ports, are expected to ship in 6 weeks. Was happy they didn’t charge any extra for the O2 ports.

Order details:

HT01    5.7L Small Block Mercruiser
CUSTOM  02 sensor inside port & starboard side manifold
FREIGHT         Freight Charge
CUSTOM  10 year warranty
CUSTOM  o2 sensor position 9" up from centre of port/bolt holes
CUSTOM  M18x1.5 Thread on o2 sensors
CUSTOM  port manifold brackets 5" (127mm) centres. use standard brackets

[MarineTorq]

Hey @justgary thanks for sharing your experience with our products! Would you mind if we used your images and experience on a social media post? 

[justgary]

1 hour ago, MarineTorq said:

Hey @justgary thanks for sharing your experience with our products! Would you mind if we used your images and experience on a social media post? 

Sure, if you want to.  Are you talking about linking to this site, or pulling content and using it elsewhere?  I'm not sure what the TOU say about pulling content.

[justgary]

1 hour ago, MarineTorq said:

Hey @justgary thanks for sharing your experience with our products! Would you mind if we used your images and experience on a social media post? 

By the way, welcome to the crew!

[AJwakedevil]

On 12/13/2021 at 9:20 PM, justgary said:

then torqued the bolts wrist tight

So is this legit? Do you only need to get them snug.. or is there an actual torque spec to get them to? I havent tried to get a wrench in there yet... but am assuming in my vlx I should have some space in there.

[justgary]

27 minutes ago, AJwakedevil said:

So is this legit? Do you only need to get them snug.. or is there an actual torque spec to get them to? I havent tried to get a wrench in there yet... but am assuming in my vlx I should have some space in there.

Torque is specified by the size and grade of the fastener.  Your exhaust manifold doesn't need to be very tight.  It has no water interface, and the back pressure should not be too high.

https://www.fastenal.com/content/merch_rules/images/fcom/content-library/Torque-Tension Reference Guide.pdf

[Woodski]

And as with any heat cycled fastener, retorque them after a few heat cycles.