2GM Mixing Elbow Question

[davejet]

Need a Yanmar Expert!
I have the orginal 2GM for my 1983 Hunter 31.
SaltWater/RawWater cooled.
The new manual Y00R0902 shows the Elbow U-type as being 128270-13600.

I have ordered a new stainless steel elbow, the mfg says it fits the same as the 128370-13600. AS you can see the fourth digit is different from mine.

I have looked at several websites online and they say only the 128270-13600 fits mine.

Does anyone know if there are any differences between these three elbows or are they all the same:
128270-13600>>>this is the only one that shows it fits my 2GM
124070-13520
128370-13600

 

[Ken13559]

I got this 128370-13600 for my 2GM20F.
http://www.ebay.com.sg/itm/331543261042?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
No problem fitting it.

 

[davejet]

This is the original 2GM which is 15hp... You have the 20 which is 18hp and considered the bored up series, which is a different beast...
But that is the one I ordered from eBay but I am concerned it may not work

 

[kloudie1]

looks like 128370-13600 is no longer made.. I am going to guess that the difference between the other two part numbers is the outlet diameter where the rubber hose connects.. They both use the same "mixing elbow joint" the left/right hand threaded connector that goes between the mixing elbow and the exhaust elbow (part bolted to engine) and they show distinctly different part numbers.. so I think the outlet nipple is what is different. The 128470-13520 is 2" and the other is not.. The book shows the 2 GMF (and 3 GMF) uses the 2" outlet but the 2 GM does not.. Measure your exhaust hose ID and if it is 2" then no problem.. if it is smaller, you'll need an adapter to use the larger outlet with your hose.(I think)

 

[wufibugs]

Did I not read on an old post on this issue that the stainless does not hold up any better, and maybe not as well as the cast elbow?

 

[davejet]

wow wish you could find the post about the stainless steel I looked

 

[Allan12210]

wow wish you could find the post about the stainless steel I looked

In my case it wasn't the cast iron that failed. It was the stainless steel connector.

Granted that e-bay one looks beefy as it is a cast part. Earlier ones on ebay were thin wall tubing and I wouldn't consider one of those. Time will tell, but keep one of these spares on board.

By the way, has anyone noticed that the output of the elbow is threaded on the inside? Mine is. If a smaller exhaust hose is being used, then could a short nipple be threaded in there and the exhaust hose be pushed over that?

 

[Ralph Johnstone]

wow wish you could find the post about the stainless steel I looked

Can't find it either but I think the bad review may have dealt with a 304 SS welded mixing elbow. Not a good idea as chloride stress corrosion is classic in weld stressed stainless. And that one looks like it's well stressed.

I'm still considering purchasing the cast 316 SS elbow as it's pretty much free from internal stress and it's half the price of a cast iron elbow up here.

 

[JamesG161]

Standard 302. 304, or 316 Stainless steel doesn't like HOT salt water. This is called chloride stress crack corrosion in stainless.

Believe it or not, it needs Oxygen to protect the surface continually. That is why SS works for rigging, winches, etc.

Cast Iron gets a protective Fe2O3 coating that looks like crap and is recommended for the mixing tee.

I inspected mine after 14 yrs of service and it was encrusted with iron oxide. My helper was about to clean it, when I said STOP!. Never clean cast iron, it formed its protective "scab".
I found no continual on going corrosion and one small dead barnacle.

If you found "point" spot wear/erosion in the old one, then it may have been galvanic and water pump streaming. If not, then corrosion failure is most likely galvanic.

Jim...

 

[JamesG161]

Sorry Ralph I breezed through to fast.

Can't find it either but I think the bad review may have dealt with a 304 SS welded mixing elbow. Not a good idea as chloride stress corrosion is classic in weld stressed stainless. And that one looks like it's well stressed.

But you can weld SS correctly and not experience the cracking.

In another post about leaking SS water tanks, one claim was the <10ppm chlorine in drinking water caused failure after 20 yrs.

If the weld was done right or as you said "no stresses", the cool water should not have failed the tank (most likely the weld).
Jim...

 

[JamesG161]

I need more coffee. It is my day for lagging thoughts.

I'm still considering purchasing the cast 316 SS elbow as it's pretty much free from internal stress and it's half the price of a cast iron elbow up here.

If you know a good welder who knows how to weld Cast Iron, this part can be welded and even put a "build up" patch of extra metal in erosion areas.

Much cheaper and probably better.
Jim...

PS: Welding cast iron is an art to avoid embrittlement.

 

[mz4wheeler]

If a smaller exhaust hose is being used, then could a short nipple be threaded in there and the exhaust hose be pushed over that?

Looking at your last photo, I bet your engine compartment gets REAL hot because of the way you connected your exhaust. Your exhaust goes through two pipe fittings before it is being cooled.

Result: Your new pipe fittings AND your exhaust manifold will get SUPER HOT from the exhaust, which will most likely lead to early failure of components in the area, like the hoses, gaskets, the manifold itself and the back end of the heat exchanger.

I assume that the reason Yanmar designed that riser was to immediately cool the exhaust to keep closed engine compartment as cool as possible.

 

[Allan12210]

Looking at your last photo, I bet your engine compartment gets REAL hot because of the way you connected your exhaust. Your exhaust goes through two pipe fittings before it is being cooled.

Result: Your new pipe fittings AND your exhaust manifold will get SUPER HOT from the exhaust, which will most likely lead to early failure of components in the area, like the hoses, gaskets, the manifold itself and the back end of the heat exchanger.

I assume that the reason Yanmar designed that riser was to immediately cool the exhaust to keep closed engine compartment as cool as possible.

it is certainly not optimum I will agree. I'm not sure if the engine compartment will be much cooler by mixing the hot water with rapidly moving exhaust gas. I'll have to ponder the thermodynamics of that one. Maybe I could wrap it with insulation up to the water injection. This was the result of a failure 5 minutes into leading a cruise-out for a week from San Francisco Bay to Monterey. We sent the fleet ahead and then since it was the 4th of July and the parts dealer was closed for 4 days, we had to come up with a fast solution. We got it done and caught up with the fleet in Half Moon Bay at midnight! By the next Sunday it was back to original and I keep the parts in case it happens again in 25 more years. I have seen other boats with similar exhausts. My friend's Newport 33 was much like that so I figured it would be okay for a while.

I have a blower on my engine compartment that runs all the time to assist in managing the temperature.

 

[mz4wheeler]

it is certainly not optimum I will agree. I'm not sure if the engine compartment will be much cooler by mixing the hot water with rapidly moving exhaust gas. I'll have to ponder the thermodynamics of that one. Maybe I could wrap it with insulation up to the water injection. This was the result of a failure 5 minutes into leading a cruise-out for a week from San Francisco Bay to Monterey. We sent the fleet ahead and then since it was the 4th of July and the parts dealer was closed for 4 days, we had to come up with a fast solution. We got it done and caught up with the fleet in Half Moon Bay at midnight! By the next Sunday it was back to original and I keep the parts in case it happens again in 25 more years. I have seen other boats with similar exhausts. My friend's Newport 33 was much like that so I figured it would be okay for a while.

I have a blower on my engine compartment that runs all the time to assist in managing the temperature.

Great on the spot repair. I don't think the insulation would help that much with the heat, but the blower probably helps a LOT. [grin]

I think the original riser design is suppose to act like a heat sink. When I point my laser temp gauge on mine, it's pretty cool (about 80 degrees) which keeps other stuff cool. You may want to consider putting the original back in the future.