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-   -   Yanmar 2GM20F mixing elbow Pearson 31-2 (http://www.sailnet.com/forums/pearson/95469-yanmar-2gm20f-mixing-elbow-pearson-31-2-a.html)

Neo* 01-05-2013 11:07 AM

Yanmar 2GM20F mixing elbow Pearson 31-2
 
The exhaust port in the mixing elbow of our Yanmar 2GM20F was 99% blocked, yet the engine was still running relatively well. She was blowing a little smoke, and this past spring the mechanic said that we should check the exhaust port because the rpm were low at full throttle. Eight months later.......

http://www.sailnet.com/forums/member...3-img-1797.jpg

We removed the exhaust elbow from the engine block with the mixing elbow still attached. The four bolts came out very easily, but getting the hose off was much tougher. We used a hack saw to cut the rubber hose and dikes to snip the reinforcing wires embedded in the hose.

http://www.sailnet.com/forums/member...-56-53-560.jpg

See the small hole just to the right of the thin metal rod. It’s about the size of an aspirin. We’ll try to chisel away the carbon so we don’t have to buy a new mixing elbow (~$185 from yanmar), but I’m not counting on it.

http://www.sailnet.com/forums/member...18-25-03-2.jpg

We sprayed with PB-Blaster and used a vise and a pipe wrench to remove the mixing elbow from the exhaust elbow. But we couldn’t subsequently unscrew the “joint”, (the double threaded pipe that connects the two elbows together), from the exhaust elbow. I plan to reuse the exhaust elbow, and now by necessity, the joint. I assume the joint can be reused…. I’ll ask the parts guy at the marina next week when I pick up the mixing elbow and the gasket for bolting the exhaust elbow to the engine block.

Can we reuse the joint? Or is it tapered and not reusable?

What gasket dressing should we use, if any?

We’ll use Teflon tape and Teflon paste when reassembling.

Faster 01-05-2013 12:24 PM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
3M, Locktite and Permatex all make a 'high temp gasket sealant' which I'd probably use rather than regular telfon tape.. I used it on our mixing elbow connections a year ago and it's holding up well.

irmedic 01-05-2013 12:54 PM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Man I feel your pain on this one. We just did the same repair in November, thankfully we could scrape the parts together in Ft.Myers. Oddly enough the boat ran well last year, then poof! Oh well it's in Nassau now. You'll be all in for $265 for parts on this likely.

PorFin 01-05-2013 05:38 PM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Neo,

Looks like both your flange and your elbow are aluminum.

You might want to try applying a little (maybe a lot) of heat to the pipe coupler (your "joint") to try and get the two apart.

As for cleaning out the inside of the mixing elbow: If it is aluminum, you'll need to be careful if you want to try boiling it out. Radiator shops usually have set ups to do this, but make sure you you talk to the owner/foreman and discuss the risk up front.

For DIY, I'd think about letting it soak in Spray Nine for a while first, to see if that helps loosen things up a bit. Carb and/or brake cleaner might also be somewhat effective.

Neo* 01-06-2013 05:53 PM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Quote:

Originally Posted by Faster (Post 971274)
3M, Locktite and Permatex all make a 'high temp gasket sealant' which I'd probably use rather than regular telfon tape.. I used it on our mixing elbow connections a year ago and it's holding up well.

Thanks, I'll look into alternative sealants. I was thinking that the exhaust would be cool enough by then, but now that you mention it, the joint is upstream of the water port in the mixing elbow.

Neo* 01-06-2013 06:05 PM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Quote:

Originally Posted by PorFin (Post 971398)
Neo,

Looks like both your flange and your elbow are aluminum.

You might want to try applying a little (maybe a lot) of heat to the pipe coupler (your "joint") to try and get the two apart.

As for cleaning out the inside of the mixing elbow: If it is aluminum, you'll need to be careful if you want to try boiling it out. Radiator shops usually have set ups to do this, but make sure you you talk to the owner/foreman and discuss the risk up front.

For DIY, I'd think about letting it soak in Spray Nine for a while first, to see if that helps loosen things up a bit. Carb and/or brake cleaner might also be somewhat effective.

The elbows do look aluminum in the picture, but by weight, they're definitely steal. The joint is stainless, I think.

The parts shop offered to use an acetylene torch when we bring it in next week, but if they tell me I can reuse it, then I don't need to remove it. As for the mixing elbow, I'll pass your de-crudding suggestions on to my buddy whose been working on it. Thanks.

Neo* 08-28-2013 02:07 AM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Update: We ended up re-using the joint (I couldn't unscrew it anyway) and the clogged elbow, after chiseling away the blockage. We used non-permanent permatex (I think that is the blue as opposed to the red) when we screwed the joint back into the exhaust elbow. We also replaced the gasket where the exhaust elbow bolts to the cooler. It was not necessary to use any treatment on the gasket.

She's been good so far this season. Starts like a charm.

Oh yeah, when I was torquing the bolts holding the elbow to the block, they felt like they were stretching too much, so I stopped rather than break one of them and order new bolts. It may have been my imagination, but better safe than sorry.

Dave Montgomery 10-21-2013 12:12 AM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
2 Attachment(s)
Here is what I did with my 3gm30. Took it out this past weekend for three days of motoring and sailing and the engine has never "seemed" to run as good! Smoother and way more cooling water and exhaust getting through. This was a cheap solution to the mixing elbow issue. It will be interesting to see how long it will last. The ports are significantly larger for both exhaust and water. Somebody questioned whether this might be a problem because of engine designed back pressure??? Well all I know is my F250 diesel wants the biggest exhaust I can get on it...

Neo* 11-07-2013 04:42 AM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Holy Crap, your a mad man.:) I like it, but I would be worried about water flowing back into the exhaust manifold when the engine is turning over but not firing, i.e. not exhaust pressure. Is there an internal pipe that carries the water past the exhaust entry?

Dave Montgomery 11-07-2013 11:49 AM

Re: Yanmar 2GM20F mixing elbow Pearson 31-2
 
Neo, I was only mad when I priced out the OEM part from Yanmar!! :-). Your concerns are valid but compensated for. Yes there is an internal pipe which extends downward from where the raw water exhaust enters at the top. This takes the raw water down past where the exhaust enters. One would figure though that even with out that internal pipe the vertical nature would take the water past the exhaust entrance. As in my post, the system has worked very well so far with about 20 hours of use. Much better engine temps, way more water getting through and far less engine exhaust congestion. Somebody mentioned engine back pressure being negatively altered but my understanding is the more exhaust flow the more GO!!


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