Exhaust Manifold Replacement - Marine Torq Stainless Steel

[justgary]

As many of you know, I ordered an HT-40 manifold set from my local Marine Torq dealer in order to prove out the process for the Group Buy going on now.  This thread documents my progress at replacing my iron manifolds with the stainless steel set.

First, a bit of background.  I use my boat nearly exclusively in salt/brackish water, so my manifolds were on a time delay fuse to rot out from the insides.  I bought the gently-used boat (a 1999 Sunsetter LX with Monsoon II engine) in the fall of 2013, and by spring had converted the engine to half-closed cooling.  This protected the block, but left the manifolds cooled with salt water.  I changed the riser gaskets and the exhaust (and fuel) hoses also.  I mainly changed the riser gaskets so I could assess the manifolds and risers and estimate about how many years I might be able to put on them.  The last thing I wanted to happen is have a leaky riser that dumped water into a cylinder, which would surely lead to a catastrophic engine failure.  I looked around from time to time, but didn't find anything available in all stainless for a reasonable price (before you tell me about them, "Stainless Marine" is aluminum with stainless risers).  I was looking and asking around this summer when I discovered the possibility of getting a group buy to help reduce my cost.

You can read more details about acquiring and inspecting the manifolds in the Group Buy, but I finally have them in hand and ready to install.  Here we go!

The HT-40 manifold set as delivered:

 

[oldjeep]

Now you are going to need a clear doghouse so you can show those off.

[justgary]

First step:  Remove the existing cast iron manifolds.  I started on the starboard side, only because that is the side nearest me when I climb into the boat when it is in the garage.  As @martinarcher found when he changed his manifolds, the bolts come out fairly easily.  I had one on each side that had a rusty head, so I had to pound a 1/2" socket onto each and get them started with a hammer and impact driver.  I'm pretty certain that the manifolds were installed in 1999 and not touched since then.

The starboard riser:

And the manifold:

I'm pretty happy that I'm doing this before next season.  The port side looks similar, and they are worse in person than the photos show.

Here is the starboard head right after removing the manifold.  Note that it does have a bit of blowby between the Siamese ports.

...and the same side after cleaning the head.  I had to remove the paint along the whole strip so that the new manifold would seat properly.  I plan to it this way without removing the heads to mill that surface, but I probably should do it now.

Here is the port side after initial cleanup.  I noticed a bit of protrusion in the cast iron head, so I had to stop and correct that by gently chipping it away and facing it with a small file.

Here it is ready to go (well, maybe enough).

[justgary]

14 minutes ago, oldjeep said:

Now you are going to need a clear doghouse so you can show those off.

I tried to get them to provide them in bead blast finish for a little less money, but they said no.  Bling it is, I guess.

[justgary]

I decided to use Permatex Ultra Copper instead of Ultra Black since it was the same price and a few hundred degrees more protection is OK with me.  I don't expect a lot of oil down there, so even if this isn't as good as the black at resisting oil, I'm probably still OK.  Here is my application on the port side.  Note that the kit comes with two studs and an allen wrench.  I put the studs in the outer set of holes (as shown) in order to help line up the other holes while I put the provided stainless bolts in.  After I had the bolts finger tight, I removed the two studs and put the bolts in.  I left it "finger tight" for an hour, then torqued the bolts wrist tight since I can't get a torque wrench on the inner four bolts.  I did use anti seize on the bolt threads.

The port side was ridiculously easy to install.

On the starboard side, I noticed that the dipstick has to pass between the mating surface and the water jacket.  This precluded the use of the stud in the rear, but it was very easy to drop the manifold over the dipstick, put it on the front stud, and then line up the rear hole without smearing the goop all over the place.  Everything so far has gone fairly smoothly.

[justgary]

Now it starts to get a bit more fun.  Notice that my raw water hoses stop at the front of the manifolds, where the cast iron ones have Gann glass-filled nylon elbows.  Notice also that the 3.5" exhaust hoses are a few inches too short since the tubes on these aren't exactly like the old risers.  I can't continue until I solve both of these issues.  I had expected the raw water hose thing, but had hoped that the big hoses were going to work.

I went to the hardware store to find a 1" brass barb elbow, but they didn't have anything that big.  They also didn't have nylon.  My plan was to use the Gann fittings in the manifold and add an elbow and more hose to get me hooked up to the water.  I think I'll drop by my marine dealer tomorrow and get longer 1" hose and go direct to the Gann fitting without an elbow.  If I don't like the way the hose lays, I can always add an elbow later.  Either way, I need more hose (roughly 2.5 feet per side).

As for the exhaust hose, I got lucky when I changed mine a few years back.  A friend with a 52' trawler had bought enough replacement hose for both of his engines, then discovered that he needed 4" hose.  He sold me what he had for $18 a foot, which was cheap even then.  I still have about six feet or so of that left over, so I'll just have to cut it and figure out how to get it on there without having to remove the manifolds again....

Finally, I have discovered the first thing on the manifolds that doesn't make sense.  Both threaded ports on the bottom (the rear one is for the zinc anode, the front is for the raw water hose) are straight thread, not tapered.  I'm not sure how I'm supposed to seal either one properly.  I'm considering an o-ring on the anode.  If it works, that's a pretty easy fix, and I won't even need to use goop on the threads (I probably will anyways).  The Gann fittings go pretty far into the front holes before they begin to get tight.  They are tapered, but they expect a tapered hole as well.  I'm still not sure how I'm going to seal them up.

Just a heads up to those of you considering this swap; you will probably need a few new hoses.  The good news is that most of you need new hoses anyway.

As for me, the good news is that these to problems kept me from firing up the engine as soon as I tightened the bolts.  At least the goop gets a day to cure now!

[Michigan boarder]

The studs for alignment is a great idea, when I did my ETX manifolds it took me a couple of attempts (and re-goops) before I got a straight on installation.

[justgary]

13 minutes ago, Michigan boarder said:

The studs for alignment is a great idea, when I did my ETX manifolds it took me a couple of attempts (and re-goops) before I got a straight on installation.

They did make the job easy.  It is already fairly easy on a direct drive where you have complete access to the manifolds, but the studs made it fairly brainless.  It was simple to finger tighten the nuts on the studs so that the holes were all aligned.  I only had to jostle it once or twice to get the bolts snugged by hand.  After that, I pulled the studs and put those bolts in finger tight and let the goop cure like the package says.

I also like that they sent a curved 11mm "Peyronie's Wrench" to use on the bolts.  It is easy to get in there with the box end to snug everything up.  With this particular manifold, I found it fairly easy to start all of the bolts and thread them by hand until they were snug. 

[Woodski]

@justgary - Those defiantly get a 10/10 on the bling meter and look amazing!  As for the straight fittings, perhaps an AN style fitting with an O ring to seal will work.  You might want to check out fittings at Home Depot / Menards for pool applications, I know they have 1" diameter fittings but can't remember if a 90 degree one is available.  The copper RTV works just fine for manifolds.  Are those exhaust manifold gaskets on the left of the manifolds in the top picture and if yes, do they have a part number on them?  Reason for question, I have D shaped exhaust ports which have a higher roof than the typical square ones.  A lot of stuff I have seen from the Aussie's can be based on older generation GM parts.  Is the actual exposed exhaust tube simply shot peened?  Should it get a shot of paint to keep it from corroding?  Do these pipes fit within the same space box of the originals, specifically height above port centers?  Spark plug access looks much better than most any other manifold, that is really a nice feature.  Nice install write up.

[justgary]

2 hours ago, Woodski said:

Is the actual exposed exhaust tube simply shot peened?  Should it get a shot of paint to keep it from corroding?  Do these pipes fit within the same space box of the originals, specifically height above port centers?

It looks more like a bead blast finish, but yes, it is the raw stainless.  I didn't think about painting that part.  I'll watch them and do it if I see corrosion forming.  I can probably hit most of that area with them mounted, but I am no longer in fear of pulling manifolds since I know the bolts will come out.

I'll check the gaskets when I get home.

[Woodski]

@justgary- thx, forgot to ask, did you happen to weigh them before install?  When in use after a few pulls and engine warmed up, might be worth shooting the uncooled part of the pipes with a temp gun just for fun and info.  Typical water cooled manifolds seem to have more water jacket down in that area.  I could see adding some heat insulation on the engine box across from that area, the gold foil stuff really works well, used in race cars all the time. 

[justgary]

7 minutes ago, Woodski said:

@justgary- thx, forgot to ask, did you happen to weigh them before install?  When in use after a few pulls and engine warmed up, might be worth shooting the uncooled part of the pipes with a temp gun just for fun and info.  Typical water cooled manifolds seem to have more water jacket down in that area.  I could see adding some heat insulation on the engine box across from that area, the gold foil stuff really works well, used in race cars all the time. 

No marking at all on the gaskets.

I did weigh them but forgot to post that.  Thanks for reminding me.  Each side is 19 pounds.  Compared to the iron manifolds and risers, which are 59 pounds per side, that is 80 pounds less weight in the boat.

Stainless steel conducts heat very poorly, so I'm hoping that I won't really see any heat issues.  On the other hand, hot spots will stay hot and cold spots will stay cold.  I'm curious about how well the outer ends of the manifolds will do with the water flow basically straight up the center.  I can't tell if they baffle the water jacket to help control flow.

[justgary]

OK, here's my plan for the elbows and anodes.  I have a few Duro 90 size 214 o-rings left over from another project, so I'm going to see if they will hold water in.  They shouldn't need to hold much pressure, but I basically don't need anything leaking inside the boat.  If this doesn't work, I'll move on to something more drastic.

[justgary]

I'm sure that my manifolds were original since I found the inspection tag still on the port elbow....

[justgary]

So I was just about to screw the first anode in with an o-ring on it when I spied the tube of goop on the floor.  Duh.  I really don't know if anodes have to make good electrical connection with the part they protect, so I only put a ring around the base.  The upper threads are free to contact whatever they want to.  It will be a simple process to remove them, inspect them, wipe them, and reinstall them with another ring of goop.

I did the same thing to the elbows.

My good friend Pat at Auer Marine fixed me up with new 1" hose, so this part is now complete.  No need for elbows in the middle of the hoses since they curve and dress nicely out of the way.  If you look closely, you can see the little ring of goop between the o-rings and the manifold pipes.

Time to remove the doghouse so I can get to the other ends of the exhaust hoses.

[Steve B.]

These look awesome ! 

Steve B.

[Woodski]

@justgary - At that point of the system there should be little to no pressure so you are most likely fine.  They are nice and light, same as the cast aluminum ones if not a pound lighter.  Looks like they will flow well also, will be interesting if you notice any effect in addition to all the engine bay polishing and cleaning you'll be doing since those look so awesome:-)

[Steve B.]

Be interesting to hear them. Also nice you'll have back-up exhaust manifolds should you need them.

Steve B.

[justgary]

On 12/14/2021 at 9:21 AM, Woodski said:

Do these pipes fit within the same space box of the originals, specifically height above port centers?

I forgot to answer this question.

I think they are actually slightly smaller.  I didn't make detailed measurements, but when I put the starboard one on it was noticeably shorter than the port iron one.  I'd say 1/2" shorter vertically.  I don't know if their manifolds for other engines would always be smaller, but from photos I have seen it looks like they try to keep them within the outer dimensions of the original manifold.  I think that one reason they are not more popular is that they 1) want you to measure your existing manifolds and provide a sketch or photos for them to verify their part number, and 2) they seem to build to order, even for their popular models.  I didn't mind waiting, and I was pretty sure from the photos that they would fit.

[justgary]

I did get a few photos to share.  You have seen the HT-40 3.5" Indmar kit above.  Here is the HT-65 Indmar manifold.  I don't know details, but it looks to me like basically the exhaust pipe has a different angle and length.  It could also be 4".

Here is the HT-01 set for small block Chevy Mercruiser with 4" outlet:

And the HT-11 SBC Mercruiser with the crazy tall riser:

[Woodski]

@justgary - Nice pics, cool they have a variety of options.  An item you will want to measure is the bottom of the highest part of the manifold relative to water level.  The last thing you want is a hydrolock event.  Two things can affect that, hot exhaust gas cooling, solved by the amount of drop in the water exit point and waterline to exhaust point.  I don't recall but as I was typing I seem to remember something posted along that line.  Of course, keeping a good set of flappers is important.  From your pics, it looks like you are fine and these are the ideal choice for a ski boat.  For the heavily ballasted gang, it behooves several measurements be taken.

[justgary]

12 minutes ago, Woodski said:

An item you will want to measure is the bottom of the highest part of the manifold relative to water level.  The last thing you want is a hydrolock event. 

I agree completely.  That is easily more important than having them fit into the same space as the originals.

From what I can see on this set, they have roughly the same rise as the cast iron set.  All the photos I have seen look like they replicated the rise, shape, and outlet from the original cast versions.  If that is the case, they should all fit well and work OK.

[justgary]

Enjoy the noise while I edit the other video.

 

[shawndoggy]

Your boat clearly wants you to take her out for a ride @justgary.

[justgary]

3 minutes ago, shawndoggy said:

Your boat clearly wants you to take her out for a ride @justgary.

Swing on by!  I've been looking for a driver so I can ski.

My wife's sister and her husband are coming for Christmas.  I may talk them into a ride.