Exhaust fabrication

[SbMolly]

I wish I took a pic to better show my current exhaust , but I imagine it’s a fairly typical setup - black iron pipe attached to a flange on the manifold, goes straight up 12 inches or so, curves back down 180 degrees, drops a few inches before attachment point for cooling water, and then large ( 2 5/8” I believe) exhaust hose off to the muffler.

The iron is in pretty rough shape - rusting away to the point that big chunks are flaking off. So I need to get this taken care of. Seems like it would be easy enough to build with off the shelf Home Depot parts - but not sure on the flange which connect to the manifold. Moyer sells a flange for $70, do I start with that, and then just buy the pipe I need? How do I seal the threads? Is it really necessary to wrap the exhaust? The old stuff is coming off all over the motor, would rather not replace.

Has anyone built, or purchased, an exhaust who can give me some pointers? Thanks.

[joe_db]

I wish I took a pic to better show my current exhaust , but I imagine it’s a fairly typical setup - black iron pipe attached to a flange on the manifold, goes straight up 12 inches or so, curves back down 180 degrees, drops a few inches before attachment point for cooling water, and then large ( 2 5/8” I believe) exhaust hose off to the muffler.

The iron is in pretty rough shape - rusting away to the point that big chunks are flaking off. So I need to get this taken care of. Seems like it would be easy enough to build with off the shelf Home Depot parts - but not sure on the flange which connect to the manifold. Moyer sells a flange for $70, do I start with that, and then just buy the pipe I need? How do I seal the threads? Is it really necessary to wrap the exhaust? The old stuff is coming off all over the motor, would rather not replace.

Has anyone built, or purchased, an exhaust who can give me some pointers? Thanks.

I have probably made 4 or 5 of them by now. You buy the flange from Moyer and the rest at the local plumbing place or McMaster. Get black iron, NOT galvanized! The zinc gives off nasty fumes when hot for some time and the fumes will make you sick.

[SbMolly]

And the section where the water is introduced - is that something a plumbing supply store could deal with? Or do I need to buy the Moyer part ($55) ?

Thanks!

[Peter]

I took my bits and pieces to the plumbing supply store to get black iron (NOT GALVANIZED) and they were able to rescue the flange and water injection point with heat and very large pipe wrenches. And some creative cursing of course!

[msmith10]

And yes, you do need the wrap on the hot section- the piping between the manifold and the point of water injection gets very hot and would be a safety hazard if left unwrapped. You can order the wrap online or at an auto parts store. Get an extra pack of the stainless steel tie wraps to keep the job neat.

[TimBSmith]

I did this riser and exhaust rebuild last season...

Machine shop help me save my Moyer Injection fitting and the flange for reuse.

I took all fittings with me to the plumbing supply store. You already have great advice on pipe type. You may have researched the black pipe vs. stainless discussions, standards, threads run deep.

I stuck with black pipe, Moyer Flange, Moyer Inline Injector Fitting https://moyermarine.com/product/inli...exht_01-1_324/. I may still install flange studs and I have to replace the lock washers I re-used because found out that the lock washer gap may allow exhaust leak. I did use high temperature pipe dope. It did help with some adjusting and disassembly that I needed to do to refit the final riser assembly. Cannot say how much I appreciate alloy pipe wrenches working in small spaces for final adjustment. I found everything snugs down about a quarter turn more than I thought.

Wrapping the pipes (minimum) and other heat shielding for safety as needed. Some have both painted their pipes with exhaust system paint and wrapped them.

Best wishes with your rebuild.

Final thoughts. I discovered my problem when water was dripping through the wrapping above the water injection spot. I discovered I also had a problem with the wet exhaust hose and replaced it around the same time. I checked the water lift muffler for any problems while I was at it. The only thing I did not do, that I have read about is an exhaust system pressure gauge fitting to help with trouble shooting from the manifold to the wet exhaust pipe.

[joe_db]

And the section where the water is introduced - is that something a plumbing supply store could deal with? Or do I need to buy the Moyer part ($55) ?

Thanks!

You can do either, I fabricated mine.
I have a T instead of a 90 degree fitting where the exhaust riser turns back down and inject the water at the top of the T. I use an internal pipe a few inches long to keep the water from being able to head back towards the engine. It is similar to this fitting: https://moyermarine.com/product/t-ty...exht_01-2_334/
If you value your time more than saving $20, I would be pretty tempted to buy this.
You can see here where the color changes where the water cools everything off:

[Dave Neptune]

If your not handy at the fabricating the MMI part will save time and frustration for a bit of cash, a great "deal" in many cases.

Also note when fabricating the pipes and fittings it is not necessary to use sealant or teflon tape. Often with the large pipe you can't get that last little bit of a turn (tightening) to point in the right direction. You can just have them snug or even a tiny bit loose. The exhaust and water will "rust, lock and seal" the fittings in place after a couple of run cycles. I have done this many times and sometimes I even used a wire to hold the pieces in place until run a few times. Then do the wrap and your ready to go. Keep the boat open when running to get things set in place.

Dave Neptune

[joe_db]

If your not handy at the fabricating the MMI part will save time and frustration for a bit of cash, a great "deal" in many cases.

Also note when fabricating the pipes and fittings it is not necessary to use sealant or teflon tape. Often with the large pipe you can't get that last little bit of a turn (tightening) to point in the right direction. You can just have them snug or even a tiny bit loose. The exhaust and water will "rust, lock and seal" the fittings in place after a couple of run cycles. I have done this many times and sometimes I even used a wire to hold the pieces in place until run a few times. Then do the wrap and your ready to go. Keep the boat open when running to get things set in place.

Dave Neptune

Note the MM part does not have to be used as shown, you only get the bronze parts. My exhaust goes 90 degrees, then up, then another 90, then into the side of a T. The top of the T gets the MM like fitting and the bottom of the T then goes down, 90 to horizontal, and then a pipe to hose fitting.
You are quite correct about the self-sealing. If you are impatient you can always run a bead of weld around the joints, but you are NOT ever going to get them full tight at the perfect spot.

[SbMolly]

Getting there, just need a hose barb for water inlet, and maybe extend one piece a couple of inches. I wish I could have found some male-female 90 degree bends - but the big box only had female-female - which adds two connections to the mix.


Thanks for the help!

[Dave Neptune]

Looks great. One "MINOR" suggestion. As the old pipe was a bit longer on the down side I will assume you have the room to add a couple of inches to the space between the top "el" and the MMI fitting. I just like the water injection further downstream so there is less possibility of "splash" going down the wrong side when starting and shutting down.

Dave Neptune

[joe_db]

Looks great. One "MINOR" suggestion. As the old pipe was a bit longer on the down side I will assume you have the room to add a couple of inches to the space between the top "el" and the MMI fitting. I just like the water injection further downstream so there is less possibility of "splash" going down the wrong side when starting and shutting down.

Dave Neptune

You beat me to it! I was going to suggest the same thing for the same reason.
Also see if you can find a street-ell for the connection into the flange. That close nipple could be a weak point.

[sastanley]

One more thing..you probably don't need an additional fitting for the water injection...look closely and those are probably not threads, and will work just fine with the hose clamped right on it.
The other nice thing is now you have a 2nd set of the flange and water injection part, so you can take your time fabricating the next replacement 4 or 5 years down the road.

[TimBSmith]

Looking good...one thought....on connectors...

I went to an industrial plumbing supply store for male/female 90 degree connectors. Wanted to limit the nipple connectors because I read that the metal is thinner on connecting nipples and I recall anecdotal comments that they represent a historical weak spot in these builds.

My build

https://photos.app.goo.gl/1jQpFckhWJseCZo17

My failure point (probably excessive backsplash at injector). Like thoughts on longer discharge section below mixing point.

https://photos.app.goo.gl/1jQpFckhWJseCZo17

Out of curiosity, do you have a picture of the failure point(s) on your old build?

Great to see your progress.

p.s.
I did a lot of prep work on the manifold seating area for the flange. I had noticed a wisp of exhaust there before I found riser problem.

p.p.s.
Did I mention that I found my exhaust riser leak the day I was suppose to launch in 2020? Doing final checks below deck and noticed a steady drip through the wrapping. Thankful I was still on my stands. Definitely rapid change of launch day plans!

[SbMolly]

My existing one has not failed yet - but I just dropped a replacement motor in, and since the exhaust looked a little rough, wanted to replace that while everything was apart.

Moving the Moyer water injection fitting down a few inches is my last step - intend to put a 2 inch straight piece between that piece, and the last 90 degree bend.

Can’t decide if i should look around for a plumbing supply store, and replace two of the bends with the proper parts, or go with the Mega low-mart all female bends, and couplers. Leaning towards a shopping trip, just need to find the time.