Exhaust Riser - Repair or Replace

Richard19068 · Jan 7, 2022

$600 is a lot of dough. I think a lot of people fabricate their own risers with black iron pipe from a hardware store. I did for my Universal M18 and it has worked well.
Looks like you might want to buy a new flange though.

Here's how one guy did it.

Building a new exhaust riser

Universal, Nipple, Exhaust Water Injected, 299693

Genuine OEM Part: Nipple, Exhaust Water Injected

discountmarinesource.com

I didn't buy the welded nipple but cobbled one together with tees and wyes.

Tom J · Jan 7, 2022

I would definitely replace that. Whether you go new or fabricate depends on your budget and/or your time. If your budget won't tolerate new, spending the time to fabricate could well be worth it. Others on this forum have fabricated exhaust elbows, mostly from SS. If you have access to a welder, I have found that ss welding rods actually flow very nicely.

markwbird · Jan 7, 2022

Replace. Any repair will only be temporary as it corrodes from the inside out. It's had it.

garymalmgren · Jan 7, 2022

Everything is repairable.!!!
An exhaust riser is not a complex piece of machinery.
The flange is reusable. (Cut off, rebore and rethread)
Maybe even the riser pipe itself.

It is joke (or a crime) to charge $600 for something like that.

Send it to Kurtis. (Just kidding)

duality · Jan 7, 2022

heres a copy of my post from a few years back, you wont be disappointed!

Got to give a shout out to HDI Marine, especially Hailey!
thursday before labor day i was fueling the boat for a lake michigan crossing the next day friday, i noticed that the mixing elbow was leaking. i had remembered that HDI offered a stainless steel replacement for the yanmar. Hailey call me back quickly and asked if i took it apart yet. which i hadnt, she recommended that i also ordered the 90 degree piece that went to the engine. she stated most get broken in disassembly. i ordered both pieces overnight. received friday morning, installed in under 2 hours and week end went on as planned. oh, with overnight shipping ($70) the total was only around $300. sweet deal!
thanks Hailey!

dlochner · Jan 7, 2022

duality said:
heres a copy of my post from a few years back, you wont be disappointed!

Got to give a shout out to HDI Marine, especially Hailey!
thursday before labor day i was fueling the boat for a lake michigan crossing the next day friday, i noticed that the mixing elbow was leaking. i had remembered that HDI offered a stainless steel replacement for the yanmar. Hailey call me back quickly and asked if i took it apart yet. which i hadnt, she recommended that i also ordered the 90 degree piece that went to the engine. she stated most get broken in disassembly. i ordered both pieces overnight. received friday morning, installed in under 2 hours and week end went on as planned. oh, with overnight shipping ($70) the total was only around $300. sweet deal!
thanks Hailey!

My first thought was to replace it.
The second was WTF? $600 to replace it?
The third was Contact HDI Marine.

DArcy · Jan 7, 2022

Look around to see if you can find a stainless exhaust, but it will likely be specific to your boat model so may be limited to Catalina direct. The exhaust on my old C&C27 was getting questionable. It was black iron pipe and lasted about 40 years (fresh water boat) so that's what I used for the replacement. The original had the water nipple welded in but I don't have a welder so I threaded the nipple in. I used high temperature pipe sealant all around. Flanges for the Atomic 4 were still readily available and the rest was from a plumbing store.

brazenarticle · Jan 8, 2022

When my exhaust riser finally crumbled I made a new one out of schedule 40 stainless pipe nipples purchased online. Luckily a friend drilled and welded the water inlet into one of the 4 inch sections, the option would have been to take that bit to a local fabricator or exhaust shop. This photo is while measuring and fitting, before the inlet installation above the silicone hose. All threads were sealed with exhaust goop and ultimately all covered with exhaust header wrap. Total cost for the stainless was under $100, I also paid for a new exhaust flange and gasket from Universal to make the job easier -

Stu Jackson · Jan 8, 2022

Ward, since ya already got it out, replace it. Good ideas here as to options of how to do it. CD sells the ss but require you to buy the insulation too, or they won't sell you the metal! It's expensive, but a good package if you don't build one yourself. Tapping in a nipple seems superior to me than the welded nipples, which are also available online as a union or piece of pipe. I've replaced my riser two or three times over the last 25 years. Make sure you (re)fit the pipe into the back of the flange with a vice; hand tight is NOT enough.

For those with Yanmars, the Universal risers are COMPLETELY different than yours. They perform the same function of mixing the water with the exhaust, but, as you see, in a completely different configuration.

Scott T-Bird · Jan 8, 2022

Yes, replace, I think. The failure at the nipple looks pretty bad. Good thing you have some time. Exploring a less expensive option may be worthwhile. Your fall-back can be the CD option if they are reliable about a delivery date.

Tom J · Jan 8, 2022

Ward H said:
I'll also call HDI Marine but their website only talks about cast pieces.

I wouldn't dismiss the idea of cast pieces entirely. If you follow best practices for diesel operation, you can get many years out of a cast system. Always warm the engine up before putting it in gear, run it hard and don't idle it too much. My 2003 cast elbow has 1600 hours on it and is in very good condition.

sail sfbay · Jan 8, 2022

If it was my sailboat I would replace it.

brazenarticle · Jan 9, 2022

Ward H said:
..I'm considering making my own out of SS. I've seen recommendations to use Schedule 80 pipe and fittings but I need to find a source. @brazenarticle Where did you source your parts?

I used 1 1/4 inch schedule 40 fittings purchased online from ZORO.com. The material is much thicker than the original riser and should last many more years. Schedule 80 seems like overkill.
If you have the room a pair of 45 degree elbows instead of one of the 90s may make fitting everything easier. I unscrewed the water muffler from the hull, moved it half an inch and reattached rather than continue messing with fitting the riser. Good to have that bit of wiggle room - the muffler is just 4 screws into plywood glassed to the hull on my boat.
Another lesson learned, don't dry fit the stainless. The threads gall easily and can be a bear to get it apart. Measure many times and assemble it all once if possible.

dlochner · Jan 9, 2022

A high temperature pipe dope should prevent galling. Galling is caused by the heat developed by friction, sometimes called cold welding.

DArcy · Jan 9, 2022

Galling is not really caused by heat but pressure combined with movement causing shear stress at the material surface. Galling is micro displacement on the material surfaces that look like fish scales. The "scales" are opposing so lock the threads in place.

Galling generally occurs when a load is applied to the fasteners during assembly, while the threads are sliding over one another. This is why locking fasteners are more susceptible than free running. Pipe threads are tapered so as soon as you start to feel resistance there will be pressure exerted on the threads. Lubricants greatly reduce galling because they reduce the shear forces on the mating surfaces. Pipe dope would probably act like a lubricant.

Stainless steels are more susceptible to galling than other materials typically used for threaded interfaces, although using two different types of stainless with different hardnesses also reduces galling. Unfortunately, you are going to be limited in material selection for pipe fittings. If the manufacturers of the fittings understood galling they would likely take this into consideration and make the pipes and the fittings from different hardness stainless.