Yanmar 2QM15 mixing elbow

[garylinger]

My U shaped mixing elbow (Yanmar 2QM15) finally blew out, big time. Fortunately I was close to the marina and didn't get too much water or exhaust inside. I ordered and received the replacement part and now for the question. I have the inverted U shaped part. At the exhaust out end it is threaded internally (despite what the Torensen Marine tech person told me - she insisted that the hose attaches to the elbow). The unit that I removed had a set of 3 pieces threaded together, a short section threaded on both ends going into the middle piece, a slightly angled (at about 15 or 20 degrees I'm estimating) and the third piece threaded into the angle with the other end being smooth for the flexible exhaust hose to attach to. These 3 pieces do not show in the parts or service manuals for the Yanmar. Does anyone here have experience with this? I'm wondering if I can use locally available plumbing pipe to thread into the elbow or is it going to be an unusual size or metric thread. Before I start running around looking for parts I was hoping to hear of anyone else's experience regarding this. I'm having a hard time unthreading things because of years of heat and rust.

 

[RichH]

What you have is probably a retrofit 'dry stack heat riser', not OEM but the injection nozzle is usually supplied (aftermarket) by most Yanmar (regional) dealers. The retrofit raises the vertical level of the injection nozzle and prevents 'backflooding' when the engine is located close to or deeper than the waterllne in the boat (somewhat like an iron 'anti-siphon loop'). Composed of: 'adapter flange' to 1.5"iron pipe nipple to iron 1.5" elbow to ~24" length 1.5" iron pipe to 1.5" iron elbow to short 1.5" iron nipple to (usually aluminum) injection elbow, etc. All is usually covered with fibrous 'lagging' to retard heat. Is this close?

Call Bayshore Marine in Annapolis, 7344 Edgewood Rd, Annapolis, MD 21403
Phone: (410) 263-8370 info@bayshoremarineengines.com
They stock the 'pipe adapter flange, the copper gaskets, rolls of 'lagging' AND a replacement (aluminum) injection nozzle. All the 'pipe' is hardware store stuff. Use hi-temp. automotive muffler cement when assembling.

 

[garylinger]

Part of what you said sounds right but a lot of it not. You are right about the anti-siphon purpose. The only part that I have/need that is NOT shown in the parts manual is the set of 3 pieces that allow for the proper angle to attach the flexible exhaust hose. I would attach a longer piece of hose directly to the elbow but I don't think it is made to attach hose to (hence the internal threading).

 

[RichH]

There can be many variations to the 'dry stack' as they are mostly 'built to fit' the existing spaces - no specific geometry nor 'instructions'.

 

[Steve Dion]

Gary: I don't know, but does this help? I changed it out several years ago. The biggest challenge was to get the damn thing apart.

http://hunter.sailboatowners.com/in...7&cat_id=25&aid=6707&page=article&mn=31_83-87

 

[garylinger]

That was interesting, thank you. You are right - the hardest part is getting it apart!!! I noticed that your exhaust hose is connected right to the elbow rather than having the configuration I have. I guess the purpose of the added pieces is to get the right angle for the exhaust hose (it does not go straight up/down).

 

[filthy liberal scum]

re; mixing elbow setup

gary;
i notice that you have a S-2, 9.2. i think you probably have the same setup as i have in my O'Day 30 since i have the same engine. others are right in that its going to be a bitch to get it apart.
the parts are as follows; first is the flange thats bolted to the exhaust manifold. then there's a pipe nipple that's screwed into the flenge, nextis a std 90deg elbow then another nipple which screws into the mixing elbow on the out side of the mixing elbow is another nipple screwed into a 30 degree elbow. then the hose adapter is screwed into the elbow. soooooo. the whole assembly has a total of 8 pieces. all are std plumbing fittings except for the flange,mixing elbow, and hose adapter.
hope this helps.

the pics by steve are for a different engine. the 2qm has a totally different set up.

 

[filthy liberal scum]

btw;
mine developed a pin hole in the side a number of years ago. i tryed to get it apart to replace the mixing ebow. could'nt get the freaking thing apart and could'nt. finally gave up and got a special welding rod for cast iron and welded the hole shut. has been fine for 10 years so i figured wtf. it works.

 

[garylinger]

Your description is exact with the exception of the angle of the elbow. I just came back from my local hardware store. I got the 3 non-standard parts - pipe nipple, 45 degree elbow and a longer than needed double threaded pipe connector (don't know what it is really called). I'm assuming that I can clamp the flexible exhaust hose to the pipe connector - between the unneeded thread and the smooth portion between the threaded ends there is plenty to clamp to. Now all I have to do is get the mixing elbow joint loose (it has rh and lh threads on either end) so I can attach the new mixing elbow. There isn't enough space to screw them together without taking them apart first! I guess I will be using a lot of heat as well as liquid wrench and elbow grease!

 

[filthy liberal scum]

gary;
you can connect the flex exhaust hose onto a standard threaded nipple or pipe end but it can be a little difficult as its slightly larger in dia than the fitting specifically made for putting a hose on it.

ps; there should'nt be any lefthanded threads anywhere in the connections.

 

[seadaddler]

Very Hard

It is very hard to get the mixing elbo apart for sure,I was lucky I new some one with a big bench vise and also some big plumber wrench's but still needed to add a long pipe to the wrench handle and sprayed lots of WD40 or some thing and I am pretty sure it has opposite treading.
Nick