Yanmar Exhaust Manifold / Heat Exchanger Corrosion

[Tellie]

It's a little tricky the way it is pictured but the majority of damage is at 9 oclock

[delmarrey]

With the core at the top is looks like 6:00 to me with some more at 3:00. I wonder where the water is being injected into the elbow, 12:00 or 9:00, if it's the square elbow???? The round elbows it's at 2:00.

[Tellie]

opps I think your right boys. I got my upside down and sideways mixed up again. A common thing for me now that I'm getting older.

[DeepFrz]

I got my upside down and sideways mixed up again. A common thing for me now that I'm getting older.

Yeah, I know all to well about that Tellie.

[Noname]

I'm not much of a diesel mechanic, or any other kind of engine guru, but does iluvteak have a freshwater cooled or saltwater cooled engine, and how did you guys know that detail?? That would make a difference, wouldn't it? Or doesn't it matter because only the saltwater is ejected via the exhaust elbow? Should saltwater be going through the exhaust manifold? I am really curious, since I have a 3gm30f.

[delmarrey]

It is a fresh water cooled system, but salt water runs thru the heat exchanger, which sits right above the exhaust. The salt water is then ejected into the exhaust elbow, which cools it. The problem being that some of the salt water runs back into the lower section when the motor is shut down. This is where the water is sitting right over the gasketed area.

If the motor has a large degree of angle most of that water should be left in the elbow.

Not sure why it's retaining the water but seems to be a common problem lately here on the forum. There could be other situations as well causing the erosion. It's had to say w/o a motor teardown right after a shutdown. It could be the wetlift is not low enough or the hull exit fitting is excepting water. Dono!

[oldcal46skipper]

Just one more example of the "superior japanese engineering" myth.

The yanmar exhaust water inject elbows are notorious for early failure. The 'certified' yanmar dealer is so happy to sell you another inferior elbow for $$$, that will also fail in a few hundred hours.

I have a yanmar powered genset that had the same problems. Before we left SoCal in 1988, I had a elbow built from thick wall stainless steel with the water flow directed into the center of the exhaust stream. Now, over 6,000 hours on the genset, it is still perfect.

Find a local machinist and have them build you a proper elbow.

Tom

[Noname]

Am I correct that the corrosion is in the manifold, not the elbow??

[delmarrey]

Originally Posted by oldcal46skipper

Just one more example of the "superior japanese engineering" myth.

The yanmar exhaust water inject elbows are notorious for early failure. The 'certified' yanmar dealer is so happy to sell you another inferior elbow for $$$, that will also fail in a few hundred hours.

I have a yanmar powered genset that had the same problems. Before we left SoCal in 1988, I had a elbow built from thick wall stainless steel with the water flow directed into the center of the exhaust stream. Now, over 6,000 hours on the genset, it is still perfect.

Find a local machinist and have them build you a proper elbow.

Tom

You can buy them prefabed>>>> Wet Ells, Exhaust Risers, Dumps, etc...

[delmarrey]

Originally Posted by Seaduction

Am I correct that the corrosion is in the manifold, not the elbow??

The elbows are eaten away by the exhaust IMO by not enough water flow. The manifolds could be a combination of both exhaust and water. It seems it depends on how the motor is set up.

[iluvteak]

Just got a look at a brand new manifold and turns out my corrosion is 360 degrees ... definitely more severe at 6 oclock tho. So scratch my 3 to 9 oclock theory.

Delmarrey may have nailed it, my engine sits pretty level fore and aft and this could cause the water build up in the exhaust mani on shutdown. My marina neighbors engine has a big time tilt to aft which could cause the water to flow out of the mani.

Its a square elbow. Water is injected to elbow directly above the exhaust port..if that makes sense. 12 oclock in other words?

Good idea on contacting Yanmar, Ill give it a try and report back. Fyi new mani was $900....obscene!

[delmarrey]

You got a deal! Yanmar 729495-44500 Sailboat Supplies, Engine Parts and Boat Parts

[iluvteak]

Originally Posted by Seaduction

Does anyone think that nonconductive gasketing and washers would be of any help?
KSC Corrosion Technology Laboratory -- Galvanic Corrosion

Seaduction ... good thought. I may try to replace the isolating gasket between the elbow and manifold with something a bit thicker than the OEM gasket. Every gasket Ive seen is a mess and probably not doing its job.

I notice you are a melbourne guy, I lived there a bit. Meg Omalleys is sweet. Love their meatloaf and cabbage. So any ideas on a material to use ?

[Maxs]

Originally Posted by delmarrey

I plan to make custom zincs, but haven't figured where to install them yet. There are a couple plug holes that I'll be checking out.

Delmarrey, did you installed the zincs already?? I have a 3jh4e, and I'm planning to install a zinc plug in the front cooler cap... Any toughts??

[rebel heart]

Had the same thing on mine but not as bad, just replaced the elbow. It's a typical replacement item on the jh series from what I've heard. You guys can bag on Yanmar as much as you want to but show me a more across the board reliable diesel that's easy to work on with spare parts everywhere. Yanmar has a lot going for me.

I have yet to find a professional marine diesel mechanic who wouldn't put a Yanmar in their own boat.