YSM12R Mixing Elbow neck

[DerekV]

Hello everyone. First post here, by recommendation from a bud at the club I'm in.

My boat has a Yanmar YSM12R engine. The other day after a surprising blow along the river, the neck connecting the mixing elbow to the engine snapped - images included:

The boat used to be an ocean boat so it is very corroded, and honestly it's on me for not having noticed sooner. I'm just glad it broke while at the dock rather than halfway to Montreal.

It's been suggested to me that I have a couple of options: I get a replacement made out of stainless steel; I find myself another YSM12R to cannibalize for parts; I post about it on this forum and pray that someone else has another idea.

If anyone has any ideas, I'd love to hear them. This boat is newish to me, and I'm not much of a gearhead, though I'm doing my best to learn as I go.

Cheers

DV

 

[Ralph Johnstone]

I get a replacement made out of stainless steel;

This will be your cheaper option from HDI Marine. A genuine Yanmar part will run you about twice the cost. Check their web site to see if they manufacture that part. Your mixing elbow will also be just about to fail or worse .......... it may be ready to leak water through an open exhaust valve and back into a cylinder which is MUCH worse.

It's costly now, but only a fraction of what the damage will be if sea water gets back into a cylinder.

 

[DerekV]

This will be your cheaper option from HDI Marine. A genuine Yanmar part will run you about twice the cost. Check their web site to see if they manufacture that part. Your mixing elbow will also be just about to fail or worse .......... it may be ready to leak water through an open exhaust valve and back into a cylinder which is MUCH worse.

It's costly now, but only a fraction of what the damage will be if sea water gets back into a cylinder.

Hmm. I tried starting the engine up before noticing the break, and when I opened the hatch to check I did see a small amount of water drip from the elbow into the engine. Should I be concerned?

 

[kloudie1]

Welcome aboard, Derek!
It looks like that mixing elbow and exhaust header have been modified.. The exhaust manifold is a female pipe thread and normally there would be a coupler that has left threads on one end and right threads on the other to screw into the pipe threads in the mixing elbow. From the picture, it looks like a pipe stub has been welded into the threaded part of the mixing elbow; the coupler is missing. It looks like there was not enough thread engagement in the exhaust header, which probably caused the crack. If you mark the orientation of the mixing elbow and the exhaust manifold, a good machine shop can either weld it all back together (no standard parts would fit) so it would be stronger and not leak.. the other option would be to either buy another exhaust manifold ($$$$) or have a machine shop duplicate the manifold which would then accept the existing modified mixing elbow. Make sure that the shop verifies the threads in the header are correct; I don't remember which has left and which has right threads.
EDIT: Water should not drip from the engine side of the mixing elbow; if it does, a whole new header, coupler, and mixing elbow would be prudent.

 

[DerekV]

Welcome aboard, Derek!
It looks like that mixing elbow and exhaust header have been modified.. The exhaust manifold is a female pipe thread and normally there would be a coupler that has left threads on one end and right threads on the other to screw into the pipe threads in the mixing elbow. From the picture, it looks like a pipe stub has been welded into the threaded part of the mixing elbow; the coupler is missing. It looks like there was not enough thread engagement in the exhaust header, which probably caused the crack. If you mark the orientation of the mixing elbow and the exhaust manifold, a good machine shop can either weld it all back together (no standard parts would fit) so it would be stronger and not leak.. the other option would be to either buy another exhaust manifold ($$$$) or have a machine shop duplicate the manifold which would then accept the existing modified mixing elbow. Make sure that the shop verifies the threads in the header are correct; I don't remember which has left and which has right threads.
EDIT: Water should not drip from the engine side of the mixing elbow; if it does, a whole new header, coupler, and mixing elbow would be prudent.

Yeah, looks to be the case. Looking at everything in the manuals and what the exhaust should look like, this is definitely all aftermarket and made by hand. The mixing elbow itself looks like sheet metal that's been welded together.

I've found this on HDI, which seems to be the part shown in the engine manual. The website says it'll fit YSM8s, but based on the shape of the attachment I think it might fit.

Regardless, I'm going to get to work on those bolts this weekend, hope to god I don't snap the bolts, and get that elbow off the engine. Then I can get a better look at everything and make a better decision.

 

[Tally Ho]

HDI makes the mixing elbow, but not sure about that neck / manifold that mounts on the engine.

I did see this one that says it will fit a YSM12…comes as a whole kit…$350.

GMKIT Stainless Steel Exhaust - HDI Marine

Replaces: Yanmar P/N 128370-13600, 128370-13610, 128270-13600, 124070-13520, 128370-13610, 104214-13521, 104214-13531, 128990-13520

hdimarine.net

Greg

 

[Ralph Johnstone]

Should I be concerned?

I'd want to take the riser off :

...................... and use a mirror to see if you can see what's inside the engine. Hopefully there will be no signs of corrosion from the leaking water you've mentioned.

 

[ggrizzard]

I bought my H30C new in 1979 that came with a YSM12F . The engine had been in salt water for 15 years when it starting having serious problems. I had it rebuilt by the Yanmar dealer in Florida. When I called the shop and asked what they found when they did the work, they said "RUST". They never mentioned doing things like flushing the engine with barnacle buster or a de-rusting solution regularly. I wish they had.
A few months later, the block rusted through and oil leaked into the water jacket.
I now have a lovely 2GM20F that's 25 yeas old. YMMV.

 

[DerekV]

Right, managed after a lot of hassle to get the riser off, and I'm now starting to wonder if someone didn't frankenstein the engine together. The crank case says "YSM12" on it, but the riser doesn't match any of the replacement parts I've seen online. Even just where the bolts go, they don't match any of what should be the replacement for a YSM12.

I've been told there may be a part number stamped onto the underside of the engine, so that's my next go. Going to take a picture of the mounting area with a tape measure held against it and send it to HDI, ask if they have any ideas.

Bloody boats, I swear... I JUST paid her off too. Figures.