Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 26-09-2021, 23:10   #1
Registered User

Join Date: Jul 2019
Posts: 18
corrosion in exhaust manifold on yanmar 3gm30f

Just purchased a new boat, and the engine survey called out some rust on the exhaust elbow and noted that it should be replaced. I ordered a new elbow and when I went to replace it, I was surprised to see the exhaust mainfold completely rusted. The mixing elbow didn't actually look that bad.

I'm planning to replace the manifold but I'm concerned that I haven't identified the root cause. Is it just leaking through the exhaust elbow? I've checked the anti siphon loop and it seems fine. I'm planning to pull off the muffler and check to see if salt water is backing up there.

Has this happened to anyone else? Any other things I should troubleshoot?

exhaust manifold



exhaust elbow


tikiavenger is offline   Reply With Quote
Old 27-09-2021, 00:03   #2
Marine Service Provider
 
Emmalina's Avatar

Join Date: Jan 2012
Location: Thailand
Boat: Herreshoff Caribbean 50
Posts: 874
Re: corrosion in exhaust manifold on yanmar 3gm30f

Looks like it coming from above . Is that your heat exchanger :? Very poor gasket made for that ..
__________________
Steve .. It was the last one that did this !
Emmalina is offline   Reply With Quote
Old 27-09-2021, 00:07   #3
Registered User

Join Date: Jul 2019
Posts: 18
Re: corrosion in exhaust manifold on yanmar 3gm30f

Quote:
Originally Posted by Emmalina View Post
Looks like it coming from above . Is that your heat exchanger :? Very poor gasket made for that ..
The first two pictures show a corroded exhaust manifold port, where the exhaust comes out of the cylinders and then is funnel through the mixing elbow. The heat exchanger is right above the corroded area, and one concern I have is coolant from the heat exchanger leaking into the manifold and hydrolocking the enine.
tikiavenger is offline   Reply With Quote
Old 27-09-2021, 00:20   #4
Registered User

Join Date: Feb 2010
Location: Australia
Posts: 1,082
corrosion in exhaust manifold on yanmar 3gm30f

If you chip away the built up crust in pic 4 youíll probably find the weld on the inner tube is corroded through to the larger raw water injection tube. Itís fairly common and is the reason why Yanmar gives this poorly designed elbow such a short service life. It can be rewelded but not easily due to the corrosion and salt. This is a cast 4LHA mixer but it gives you a clue to where the raw water gets through. Click image for larger version

Name:	IMG_2684.jpg
Views:	75
Size:	264.0 KB
ID:	245964
skipperpete is offline   Reply With Quote
Old 27-09-2021, 05:19   #5
Marine Service Provider
 
Emmalina's Avatar

Join Date: Jan 2012
Location: Thailand
Boat: Herreshoff Caribbean 50
Posts: 874
Re: corrosion in exhaust manifold on yanmar 3gm30f

still looks like the heat exchanger is leaking but the elbow is so thin i would make another one out of SS but depends on how your welding is LOL
Is it mild steel or cast iron ?
__________________
Steve .. It was the last one that did this !
Emmalina is offline   Reply With Quote
Old 27-09-2021, 06:16   #6
Registered User

Join Date: Aug 2015
Location: Savannah Ga USA
Boat: Brewer 12.3
Posts: 92
Re: corrosion in exhaust manifold on yanmar 3gm30f

The elbow was spraying water into the manifold. The Yanmar is crap. There is a company making a cast manifold that is much better. The Yanmar is not repairable. The inner tube is pitted and you'll find pitting everywhere.
Cause is heat+ exhaust gases + sea water make material choices tough and corrosion imminent. lovely mixture of acids, chlorine.
I had the same problem on mine.
Oldwheels is offline   Reply With Quote
Old 27-09-2021, 09:44   #7
Registered User

Join Date: Jul 2019
Posts: 18
Re: corrosion in exhaust manifold on yanmar 3gm30f

Quote:
Originally Posted by Oldwheels View Post
The elbow was spraying water into the manifold. The Yanmar is crap. There is a company making a cast manifold that is much better. The Yanmar is not repairable. The inner tube is pitted and you'll find pitting everywhere.
Cause is heat+ exhaust gases + sea water make material choices tough and corrosion imminent. lovely mixture of acids, chlorine.
I had the same problem on mine.
Oof Ok. I guess I'll plan on checking the elbow yearly, and planning to replace at the soonest signs of rust/corrosion inside, so I can save my new manifold. Anything else I can do? A friend suggested I flush out the raw water system with fresh water after each time I use it, but that seems like such a hassle.
tikiavenger is offline   Reply With Quote
Old 27-09-2021, 16:56   #8
Registered User

Join Date: Feb 2010
Location: Australia
Posts: 1,082
Re: corrosion in exhaust manifold on yanmar 3gm30f

If you lay up the engine for storage, by all means run it on Fresh water to displace the raw water in the heat exchanger and aqualock, some add coolant conditioner when doing the flush, but for normal usage itís probably of little value to flush out the system on a regular basis.
If you see corrosion on that mixer elbow (as in pic 3) then you have a problem or at best, a warning. There is no way that salt water corrosion should be present on the gasket seam or the weld on the mixer flange, yours was actually dripping water onto the lift pump directly below.
skipperpete is offline   Reply With Quote
Old 27-09-2021, 17:55   #9
Registered User

Join Date: Feb 2006
Location: Eastern Caribbean for the 2020 season then east coast or Panama
Boat: Lagoon 470 cat
Posts: 608
Re: corrosion in exhaust manifold on yanmar 3gm30f

The manifold doesn't look that bad to me. Little wire brush and clean it up. The mixing elbow is not terrible and to me it is repairable. Had one that the inside was completely separated. Took it to a muffler shop and they welded it for $10. Have a few hundred hours on that elbow since then, although i do have a spare onboard in case it fails.



Given that the manifold just looks like surface rust to me I would just clean and inspect it before replacing.



As other have mentioned, it also looks to me line the water is coming from on top or the manifold. I would defintely check/replace the gasket on the heat exchanger.
Moontide is offline   Reply With Quote
Old 27-09-2021, 20:04   #10
Registered User

Join Date: Jul 2019
Posts: 18
Re: corrosion in exhaust manifold on yanmar 3gm30f

Quote:
Originally Posted by skipperpete View Post
There is no way that salt water corrosion should be present on the gasket seam or the weld on the mixer flange, yours was actually dripping water onto the lift pump directly below.
Hmm, I guess I'll keep a close eye on the lift pump and perhaps get a spare ready for when that goes.
tikiavenger is offline   Reply With Quote
Old 27-09-2021, 20:06   #11
Registered User

Join Date: Jul 2019
Posts: 18
Re: corrosion in exhaust manifold on yanmar 3gm30f

Quote:
Originally Posted by Moontide View Post
The manifold doesn't look that bad to me. Little wire brush and clean it up. The mixing elbow is not terrible and to me it is repairable. Had one that the inside was completely separated. Took it to a muffler shop and they welded it for $10. Have a few hundred hours on that elbow since then, although i do have a spare onboard in case it fails.



Given that the manifold just looks like surface rust to me I would just clean and inspect it before replacing.



As other have mentioned, it also looks to me line the water is coming from on top or the manifold. I would defintely check/replace the gasket on the heat exchanger.
I ended up replacing the entire manifold just to be safe, but maybe I'll wire brush it and see if it improves. I was mainly worried about the surface not being flat/clean, to make a seal with the exhaust elbow gasket.
tikiavenger is offline   Reply With Quote
Old 27-09-2021, 20:20   #12
Registered User

Join Date: Feb 2010
Location: Australia
Posts: 1,082
Re: corrosion in exhaust manifold on yanmar 3gm30f

Wow, thatís the heat exchanger and all,I like your style. Usually itís enough to just file the manifold face flat but your one had more corrosion than usual so ... good call.
skipperpete is offline   Reply With Quote
Old 28-09-2021, 05:14   #13
Registered User

Join Date: Apr 2010
Location: Canada
Boat: C&C
Posts: 288
Re: corrosion in exhaust manifold on yanmar 3gm30f

It looks just like mine did every few years, normal for Yanmar and good advice from Oldwheels and Moontide. Yours definitely had a pinhole leak as I can see by looking at the 3rd and 5th pic down. I did silver solder one of mine from the outside and tried it out, then kept as a spare. The rust on the manifold looks no where as bad as mine was. I just used a good grade of Permatex hi temp gasket repair and it sealed no problem. Did that for many years. Have fun!
wannacat is offline   Reply With Quote
Old 28-09-2021, 15:56   #14
Registered User

Join Date: Jul 2019
Posts: 18
Re: corrosion in exhaust manifold on yanmar 3gm30f

Quote:
Originally Posted by wannacat View Post
It looks just like mine did every few years, normal for Yanmar and good advice from Oldwheels and Moontide. Yours definitely had a pinhole leak as I can see by looking at the 3rd and 5th pic down. I did silver solder one of mine from the outside and tried it out, then kept as a spare. The rust on the manifold looks no where as bad as mine was. I just used a good grade of Permatex hi temp gasket repair and it sealed no problem. Did that for many years. Have fun!
Interesting about the manifold. My mechanic warned me that there is corrosion between the heat exchanger area and the exhaust manifold, and that if i didn't swap out the manifold, I could risk having coolant drain into the engine and hyrdrolock it. Is there any validity to that?
tikiavenger is offline   Reply With Quote
Old 28-09-2021, 18:38   #15
Registered User

Join Date: Feb 2010
Location: Australia
Posts: 1,082
Re: corrosion in exhaust manifold on yanmar 3gm30f

Your mechanic is absolutely correct. Not as common as cylinder flooding with salt water but definitely a source of hydrolock damage.
skipperpete is offline   Reply With Quote
Reply

Tags
3gm, 3gm30, corrosion, exhaust, yanmar

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Yanmar 3GM30F mixing elbow and exhaust manifold question Copacabana Engines and Propulsion Systems 18 12-10-2019 23:30
Yanmar 3GM30 Exhaust Manifold Aussie_Sequoia Engines and Propulsion Systems 5 08-11-2012 07:46
Yanmar Exhaust Manifold / Heat Exchanger Corrosion iluvteak Engines and Propulsion Systems 48 22-10-2012 09:09
Yanmar, factory assembled, no exhaust manifold gasket! boden36 Engines and Propulsion Systems 0 04-08-2012 22:09
Yanmar Exhaust Manifold Corrosion Jerry45 Engines and Propulsion Systems 14 30-10-2011 17:29

Advertise Here


All times are GMT -7. The time now is 04:33.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.