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Old 10-09-2012, 05:48   #1
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Yanmar 3GM30 Louder, Smokier?

Just a quick question: Maybe I'm just paying too much attention, or maybe I'm simply crazy, but is it possible for my Yanmar to start sounding louder at the exhaust port and to be smokier without any obvious loss in performance?
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Old 10-09-2012, 05:52   #2
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Re: Yanmar 3GM30 Louder, Smokier?

sure, check the water supply/strainer
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Old 10-09-2012, 06:05   #3
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Re: Yanmar 3GM30 Louder, Smokier?

Thank you, Don! Displaying my ignorance fully for all the world to see, please allow me to confess that I didn't know I had one. I'm very happy to work on the engine, however. Where can I find that rascal?
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Old 10-09-2012, 06:33   #4
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Re: Yanmar 3GM30 Louder, Smokier?

Check to see the amount of water is flowing out of the exhaust. If its weak and misty, the most obvious restriction will be the exhaust elbow being coked up. This elbow ( bolted directly to the manifold) has a recommended replacement every 2 - 3 years. Not necessary if you remove it and acid wash it. Muriatic acid bath for 5 minutes and then lots of flushing with water.

To test if the elbow is choking off the water supply, the quickest way is to remove the discharge water hose from the elbow and check the flow while the engine is running. It should be very strong. If its weak and dribbly then you can go back upstream and check the raw water pump for a bad impeller.

Been there with this problem twice so far....First time I didn't acid wash, just cleared it by beating it on the dock and used a wire to scrape inside.
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Old 10-09-2012, 06:55   #5
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Re: Yanmar 3GM30 Louder, Smokier?

If the elbow is restricted it probably would also result in a loss of power. And if you run the engine long enough with low cooling flow it will lead to increased scale build up in the exhaust elbow.

Dennis, follow the line from your seawater inlet to find your strainer (if you don't have a strainer you NEED to get one). And I hate to just snipe at you, but if you don't know where these are you need to spend some time tracing out all your lines as you need to know where all your fitting/vlves etc are.
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Old 10-09-2012, 07:13   #6
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Re: Yanmar 3GM30 Louder, Smokier?

Hi Dennis, had similar issue w my yanny,so agree with above posts. Good to see you back here; been wondering if your dog ever recovered from your misadventure in Buzzards Bay. I've so traumtized my dog that he will not even get out of the car when I park here at Norrie Point marina. I suspect you are the same Dennis M. that I knew years back in N.P.............If so ,regards
Mike Rohr
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Old 10-09-2012, 07:52   #7
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Re: Yanmar 3GM30 Louder, Smokier?

Quote:
Originally Posted by terrylad View Post
Check to see the amount of water is flowing out of the exhaust. If its weak and misty, the most obvious restriction will be the exhaust elbow being coked up. This elbow ( bolted directly to the manifold) has a recommended replacement every 2 - 3 years. Not necessary if you remove it and acid wash it. Muriatic acid bath for 5 minutes and then lots of flushing with water.

To test if the elbow is choking off the water supply, the quickest way is to remove the discharge water hose from the elbow and check the flow while the engine is running. It should be very strong. If its weak and dribbly then you can go back upstream and check the raw water pump for a bad impeller.

Been there with this problem twice so far....First time I didn't acid wash, just cleared it by beating it on the dock and used a wire to scrape inside.
Both times my exhaust elbow restricted the water flow without affecting the exhaust flow. Internally the elbow is an open pipe to the exhaust and is unlikely to choke the flow. The water side is highly subject to restriction due to scaling, however. The bottom line is, if you've got plenty of water pressure to the elbow and little output - that's your problem. Briefly pulling the hose off the elbow while the engine's running tells you immediately whether the problem is upstream or downstream.....
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Old 10-09-2012, 08:42   #8
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Re: Yanmar 3GM30 Louder, Smokier?

I have a Yanmar 2GM20F in an 8000 lb sailboat. I hear much about soot restriction problems in the exhaust elbow. I have been operating 10 years and 2100 hours. I try to run the motor at high output fairly often (as recommend in the manual) and I have inspected the fitting where water is injected into the elbow. I have had no soot problem that I am aware of. The question is, are there many others who run for many years without any special maintenance of the exhaust or am I just lucky?
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Old 10-09-2012, 09:44   #9
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Re: Yanmar 3GM30 Louder, Smokier?

Evening tide, if you want to start a poll it should be in a separate
thread.
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Old 10-09-2012, 10:03   #10
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Re: Yanmar 3GM30 Louder, Smokier?

Thanks everybody!

Terry, I had the exhaust elbow replaced two seasons ago. The water being emitted from the exhaust port is definitely strong. I wanted to replace my impeller at the beginning of the season, but didn't get to it. Another ignorant question: wouldn't I see overheating if my impeller is bad?

Don, I fiddle with the sea water inlet hose every time I winterize the engine. I've never seen a strainer. That doesn't mean there isn't one. I've just never noticed it. I'll certainly check it this coming weekend.

Thanks again everyone!
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Old 10-09-2012, 10:12   #11
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Re: Yanmar 3GM30 Louder, Smokier?

The only thing that's left is the muffler, I guess. If you've got good exhaust water coming out, then that would eliminate everything back down the line. Other than a constricting line around the prop shaft, which would affect your power and produce darker smoke, I can't think of anything else that would make the exhaust louder.

If its not there, I'd definitely install a seawater strainer BTW. Those heat exchangers are prone to clogging easily.
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Old 10-09-2012, 10:20   #12
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Re: Yanmar 3GM30 Louder, Smokier?

One thing I haven't seen mentioned thus far is a possible problem with the injectors. Fouled injectors will produce smoke. And if not fouled enough, you may not notice a loss in performance.
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Old 10-09-2012, 10:23   #13
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Re: Yanmar 3GM30 Louder, Smokier?

There's a muffler? Geez...I've never seen that either.
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Old 10-09-2012, 11:51   #14
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Re: Yanmar 3GM30 Louder, Smokier?

Sorry DeepFriz, I am new here. This thread seemed to have exactly the audience that could offer advice to me.
In response to the original question about loud exhaust and smoke, I had this happen a few times when I had an air lock in the raw water pump and no water was flowing. It was so obviously loud that I noticed and shut down the motor immediately.
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