Jump to content

Exhaust manifold & mixer


Recommended Posts

Sadly the exhaust manifold and mixer on my engine has reached the end of its life and has failed fairly dramatically.  The engine is an older Isuzu and the original cast iron manifold has corroded fairly dramatically to the point where it broke (fell) in half while dismantling. You will see in the attached photo there is a stainless water jacketed riser and mixing elbow which are custom made. The water jacket is really just a second point of injection into a well which the exhaust gases flow through, rather than a proper jacket.

Parts for the Isuzu are hard to come by, so it looks as if we will need to fabricate a new manifold. An engineer mate who looked at the current setup is worried that salt water sitting in the bottom of the hot riser causes water to condense inside the manifold when it cools, and has rotted it from the inside out. It certainly looks as if that could be the case.

I'm wondering if this sort of exhaust setup is very common, and whether there might be a better way of doing it given that I am pretty much going to need to start from scratch.

Thanks for any thoughts or advice. (The engine is in reasonable condition apart from this, so not considering a repower.)

Exhaust 2.jpg

Exhaust 1.jpg

Link to post
Share on other sites

We just ordered a new stainless exhaust elbow for our Perkins from these guys : https://hdimarine.net/ - they make a after market Yanmar elbow (which is what is on the Perkins).

The prices are much cheaper than a genuine yanmar part even with shipping and they are a family business who I found helpful on the phone. Part should arrive this week - will let you know.

 

Link to post
Share on other sites

Fabricate a new one out of steel and do away with the S/s 2 dissimilar metals,trouble,made on for a yanmar out of galv water pipe 50mm still going 6 yrs on.

Link to post
Share on other sites

I agree with Harry Tom, whatever you decide on avoid welding dissimilar metals., try and use a bolted flange where  Cast Iron meets Stainless Steel.

I have fabricated exhaust elbows using  threaded pipe elbows, nipples and such from ANZOR, they were in expensive, the range is huge. 

A local fabricator welded the seams once assembled, the flanges were laser cut, good luck !

Link to post
Share on other sites
9 hours ago, bigal.nz said:

We just ordered a new stainless exhaust elbow for our Perkins from these guys : https://hdimarine.net/ - they make a after market Yanmar elbow (which is what is on the Perkins).

The prices are much cheaper than a genuine yanmar part even with shipping and they are a family business who I found helpful on the phone. Part should arrive this week - will let you know.

 

+1  Bought one of these five years ago as a backup to the OEM.

Wall thickness greater, far superior imo.

Murphy's waiting for me to forget about this potential problem.

Thanks!

 

 

 

 

Link to post
Share on other sites

Lees marinised most of those old Izuzu's (we had one). They may have knowledge that would help. We had them refurb our water pump. That said, they would need to fabricate an exhaust elbow anyway. But they may have the knowledge to make it work first time. That set up you had certainly does look fairly random.

Lees are still operating, I get mixed up if it is Lees Engineering, or the outfit that sells engines, but contact the first one you find on google and they'd put you onto the right people.

Link to post
Share on other sites

Thanks for the replies.

I have somebody lined up to help with the fabrication. He's a first class welder and machinist, though not much marine experience. We have a plan for making a new manifold and intend to keep that separate to the riser and mixer to make future repairs easier.

I'm still not happy with the idea of hot salt water sitting in the bottom of the riser and condensing into the exhaust manifold as the engine cools, so I'm keen to see if there's a better way to do it. The previous owner had exhaust valve problems and had to do a head overhaul, so I suspect the current setup is causing problems. Bigal, I'll be interested to hear how you get on with the aftermarket Yanmar elbow. It could be a possible option. Otherwise we will have a go at building something.

I've been wondering if a mixing elbow alone will be sufficient, and do away with the riser. One concern is getting enough cooling before the plastic muffler. It's quite close to the elbow and can't easily be moved. Any thoughts on how far away the muffler should be for the mixer to have done it's work? I checked the Vetus manual for the muffler but it wasn't much help - just says to keep below 70 deg C and connect to metal exhaust via a reinforced rubber pipe.

There are some good options for bends and fittings at ANZOR and Steel & Tube stainless. Any thoughts on using standard seamed bends verses Schedule 10 or 40 seamless, or just threaded BSP pipe fittings like the one Frank made?

Link to post
Share on other sites

I think if you need to be asking questions like that, it would be easier and lower risk to get an off the shelf item. The risk part being melting something after having done all the work.

The Engine Room have a range of elbows available. They are the Beta agent. I don't have any pictures handy, but they have high rise elbows, cross overs (going from one side of the engine to the other),  High rise with a cross over, standard elbows, slight rise with an offset, etc. Several options are made out of alloy, so they don't cost moonbeams. They have shop drawings for all, so you can suss the geometry you need to get it to fit as well.

These ones are known to work, cool the exhaust adequately, etc, oh, and fit standard exhaust hose etc.

Cost was reasonable. Depending on the option I think less than $400, but don't quote me, it changes for every option.

If you are interested, I have shop drawings on my other laptop. Or ask them.

https://www.theengineroomltd.com/beta-marine

Link to post
Share on other sites

The expelled raw water should inject on the downhill side of the riser like the diagram in this link (https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/) In my opinion there should not be pooled water anywhere near the riser after engine shutdown, if there is then I'm sure its going to cause problems.

I agree with Fish that using off the shelf components is a good option but clearly they must be sized for your engine and the assembled configuration suitable for your installation. I'm sure most technicians will give you appropriate advice when purchasing from them, but its all on the web as well.

The reason I fabricated my own was that Volvo wanted $800 for a lousy cast iron mixer elbow for a 20 Hp engine ! A part that I knew from bitter experience would not be particularly durable. Stainless steel will not last forever either (crevice corrosion) but It should significantly outlast cast iron. The ANZOR fittings I used were cast SS which I think should outlast Seamed Pipe. ( I don't trust the seam) .

I melted my plastic muffler twice and in both cases it was because  someone forgot to open the raw water intake valve ! Otherwise it never gave rouble so long as raw water was being injected into the the elbow. It caused the engine no harm as it melted way before  before the engine over-temp sensor triggered.  You are left with a filthy mess to clean up in the engine bay and the engine is inop until you replace the muffler box.

If time is on your side and you suffer from technical OCD use monel or inconel, it will out last the engine. 

 

 

Link to post
Share on other sites

Thanks again for the replies. 

Fish, the contact for The Engine Room sounds worth a follow up and Frank, that was a useful link you provided. All good info.

I'm breaking the job into two parts. The first is to fabricate a new manifold for the engine, replicating the original one as closely as possible, but in stainless.  While we are doing that I'll investigate the options for the riser and mixing elbow. There's a bit of a plan taking shape, so I hopefully I'll be able to share some photos before too long (and be back on the water).

Link to post
Share on other sites
7 hours ago, lateral said:

Just checked my OEM Yanmar mixing elbow (new 2015) just starting to show scale on junction with mount plate.

Time to fit HDI one.

Ours arrived last week and we are very pleased, the DHL shipping was fast with regular email updates right to the front door. Its a shame they don't make Volvo D1-20 stop solenoids LOL.

Link to post
Share on other sites
On 30/01/2021 at 6:29 AM, Frank said:

Ours arrived last week and we are very pleased, the DHL shipping was fast with regular email updates right to the front door. Its a shame they don't make Volvo D1-20 stop solenoids LOL.

If you have a close look at your solenoid you will most likely find it is made by Bosch or one of the other big OEM suppliers. Should be able to find one that does not have a "green" price.

Link to post
Share on other sites
3 hours ago, marinheiro said:

If you have a close look at your solenoid you will most likely find it is made by Bosch or one of the other big OEM suppliers. Should be able to find one that does not have a "green" price.

Good call, the update is the solenoid is confirmed as US, it remains "Sticky" even after some freeing, I reckon something has failed inside. Its a Shibura Motor so that will be the first search thread, I wont even bother looking up Volvo.

Link to post
Share on other sites
Just now, Frank said:

Good call, the update is the solenoid is confirmed as US, it remains "Sticky" even after some freeing, I reckon something has failed inside. Its a Shibaura Motor so that will be the first search thread, I wont even bother looking up Volvo.

I should add that I reinstalled it with the core retracted so the motor is back on line we just stop it with the mechanical cutoff lever for now, at lease we can go cruising again :-)

Link to post
Share on other sites

I promised I would share some photos so here they are. New exhaust manifold fabricated from Schedule 40 pipe and the exhaust pipe and mixing elbow. Fitted it all up and tried it out on Saturday and it works perfectly.

Manifold.thumb.jpg.80fcb7d29d639b8c1b2c25be48c6f8fc.jpg

Mixing elbow.jpg

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...