3GM30F exhaust elbow tip

[Bob 04 H260]

Our engine is 10 years old and has 400 hrs on it. As far as I know the mixing elbow is original.
I was at the local Yanmar dealer last week and asked about the expected life span of these elbows. He said their mechanics often change them after about 5 years in the Florida salt water. I asked about the price and he suggested I look at a "take-off" to save money. These are parts that have been taken off of a new engine because this exhaust will not fit in a new boat. They are sold at a discount.
I bought the mixing elbow, the double ended threaded connector, the cast exhaust manifold and gasket for $232. From what I have seen posted it seemed like a good deal. I will pull ours off at the end of this season and if ours is fine I will just put it into the parts inventory. If not it will be an easy swap with all new parts

Bob

 

[frank balcer]

Bob, just changed this part this past winter. Be real careful taking the old one apart as one end of the connector has left hand threads. Unbolted the assembly from my engine and put it in a vice, promptly cracking the upper piece as i was going the "wrong" way while dissasembling the three pieces.

 

[Steve Dion]

Bob: I think that is an excellent price. Did he ever give you the retail price for the parts?

If you attempt to take the manifold/elbow apart I suggest that you get a torch to heat up the parts (welders torch does it better/faster). You do need to be careful of the reverse threads, but you should be able to tell which way the are attached.

Be sure to use never-sieze on the threads for the new one as well as the old one. It also helps if you have some gasket glue to hold the gasket in place if you have bolts that screw into the head vs studs sticking out of the head.

PS: Our boat lives in fresh water and makes occasional trips to the saltwater (good for cleaning the bottom). I replaced our elbow on our 2gm after about 8-10 years and there was not any clogging.

 

[navigator97]

Bob, In salt water operations I have heard, and have experience that agrees, that it should be changed out after about 500 Hrs. of engine use. Since you are planning to take it off, it would certainly be the time to put on the new one, even if the old one looks ok. I have changed ours every 500 hours or so. and it needed it. You will also find a noticable drop in fuel GPH consumption. On my 2GM20F Yanmar, i get up to about 0.45 GPH when it's about 500 Hrs. and it drops to about 0.30 GPH with a new Mixing Elbow.

 

[Bob 04 H260]

Thanks for all the great advice. I do have a welding torch at home and will use it if needed when I take the old one apart. When I ordered the parts the dealer said the saving where over a $100 on the two cast pieces, the gasket and threaded piece were the regular price.

I will be quite interested to see how much we have for deposits in our mixing elbow. While it is 10 years old the boat has only been used in salt water for about 18 months.

I read some place that the mixing elbow deposits increase when the sea water temperature goes above 150*F. Makes sense if you are having any conversion to a vapor it will leave some minerals behind. That might explain why some boats have a lot of deposits and others none. I may try to measure my mixing elbow temperature with the infrared thermometer and see what it reads. I guess the critical temperature is on the inside surface, but if the outside is approaching 150 I can be sure the inside will be well above that.

When I changed the hoses on the engine I made them a bit longer to reduce the radius of the bends in the hope it might increase water flow through the mixing elbow. I think the new Speed Seal Life for the raw water pump may improve water flow through the mixing elbow as well.

If an engine is having more deposits than expected it could be a good argument for an annual impeller change as wear on the impeller must reduce water flow through the elbow as well.

............just a few rambling thoughts this morning while sitting in the cockpit drinking coffee, Bob

 

[Calif. Ted]

I'm pretty sure the 3 pieces and gasket cost me $352 US last time I changed it.

 

[Steve Dion]

Bob: I believe that running the engine at lower RPM (less than 70% of max rated RPM) will also increase the chances of carbon/coking build up in the elbow.

Check out the YanmarHelp website. The owners no longer maintain it (last time I checked) but the infor is still helpful.

 

[Bob 04 H260]

Thanks for all the good information guys. I will be hauling the boat in May and once back on dry land I will pull the old elbow and see what is inside there. I think I will just put the new one on and if the old one is usable keep it as an emergency spare. With all the tools and spares I am collecting I may have to re-paint the waterline !
Bob