3 gm 30 mixing elbow issues

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
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soundboy
Posts: 4
Joined: Sun Dec 21, 2008 1:33 pm

3 gm 30 mixing elbow issues

Post by soundboy »

hi all
I have a f 33 w/ the yanmar 3gm30 engine
I started the engine the other day and saw that there was no water getting through with the exhaust. Checking into it I find that the 90 degree elbow is clear, there is plenty of water flow through the water line but it's not getting injected into the exhaust. So there is a internal clog in the elbow.
The mixing elbow is the original unit that came with the boat,
I know it will need to be replaced but it doesn't look like fun,
has anyone had experiences replacing the mixing elbow,
I did see this post in the archives
http://freedomyachts.org/viewtopic.php? ... haust#p243
looks like mine but not as much corrosion

al mcguire
tanstaafl
jacksonville fl

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JimD
Posts: 46
Joined: Mon Dec 15, 2008 1:38 pm

Re: 3 gm 30 mixing elbow issues

Post by JimD »

Al,

On my 30GM30F I replaced the elbow every five years. I took the complete assembly off of the maifold and took it to a diesel mechanic and he took it apart and replaced the mixing elbow. He put the two pieces back together using a "long" piece of pipe as a lever. I always waited for it to break into little pieces, it never did. All you then need is a new gasket for the maifold.

The five years came for a diesel maintance course I took when I first bought the boat. That and replacing the raw water pump impeller every year were two suggestions as preventive maintance. It worked for me.

Jim Demerest
Lady of Remes
F36/38

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Robert
Posts: 43
Joined: Thu Dec 04, 2008 9:44 am
Location: Arapahoe, NC / Norfolk, VA

Re: 3 gm 30 mixing elbow issues

Post by Robert »

Question, you did check your raw water pump impeller first!!

I only ask as you did not mention it in your initial question, check closely, even if it has all it's vanes it is possible for them to loose the rubber bind to the shaft coupler. Also make sure you have no thru-hull or strainer blockage.

I am not saying the elbow is not blocked, but there are things before the elbow that can also stop water flow.

On the subject of changing the elbow, if your is like the one shown in the thread you linked to, the U part at the top is actually left hand threaded, the elbow itself is right hand threaded and the coupler between obviously both, the coupler acts in a similar manner to a turnbuckle and will pull the two parts in together or push them apart if rotated the other way. If, as you say, they are original, I would change the 3 parts out, they are held to the heat exchanger / manifold outlet by 4 x 8mm bolts (2 different lengths), use a 13mm socket to remove them after giving them a real good soaking with PB Blaster or your preferred penetrating fluid, you will probably have to replace these fixings. Expect to pay around $32$5 for these 3 parts and a gasket.

I will be replacing my elbow in the next month or so...
Robert

s/y 'Magic' - 1985 Hoyt F32

soundboy
Posts: 4
Joined: Sun Dec 21, 2008 1:33 pm

Re: 3 gm 30 mixing elbow issues

Post by soundboy »

robert and james
thanks for your quick replies

we did check the water flow and there was lots of water, filled up a 16 oz container very quickly

I have also been spraying blaster on the bolts and threads, I even let some sit in the water injection inlet and it has started to pass slowly through
I have accepted the part needs replacing
how difficult is it to remove those 4 bolts that hold the manifold to the engine block ?
how well do they come out after soaking in blaster for a few days ?

al

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