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Discussion Starter · #1 ·
I don't have any water coming out my exhaust all of a sudden? It is 'raw' water cooled sb8 Yanmar Diesel. I took the hose loose at the ball valve and water poured in. Cleaned the strainer, checked the impeller, nothing broken, it's soft, this just happened, any ideas where to look next? Thanks.
 

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Either the impeller is bad, could look ok but spun on hub, or there is a blockage up stream from the impeller. On a raw water engine this could be scale. Try back flushing the engine w/ a hose.
Jim
 

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Either the impeller is bad, could look ok but spun on hub, or there is a blockage up stream from the impeller. On a raw water engine this could be scale. Try back flushing the engine w/ a hose.
Jim
I'm no mechanic, but couldn't the blockage be downstream as well? I'd double check your impeller to make sure it is mated to the shaft.
 

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Check where the water enters the exhaust elbow. Corrosion and salt deposits often clog the little port. Usually it's easier to just replace the elbow than to try cleaning it out and rehabbing it, since by the time it gets clogged up the corrosion is pretty well advanced.
 

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This is going to very sound silly...but before you tear things apart..squirt some dawn dish detergent into the line ahead of the impeller, maybe at the strainer for you.

That happened to me once...for no apparent reason. I checked every possible cause to no avail. My boat neighbor said " squirt some dawn in thar" and it worked..I suddenly had plenty of flow..and suds coming out the exhaust. Don't ask me why it works..I'm guessing it adds a little lubrication to the impeller and helps creates better suction. Once I did that, I was fine all season. If that doesn't work..go to plan B
 

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Basically two choices - pump not pumping or a blockage. Just go step by step through the system. Since this happened suddenly and you say the pump looks good, I would lean towards a blockage.
 

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Also check exhaust manifold for release of 'slab rust' which easily migrates to and blocks the exit ports of a failing manifold. To check, remove and invert the manifold and 'shake it'. (note- once an exhaust manifold begins to develop 'slab rust' the potential becomes very great that there will also be a 'pin hole' develop between the 'gas side' and 'the water side' of the manifold ... and water then can easily 'backfill' into a cylinder)

Also check the water pump for integrity of the CAM that the impeller 'rides against'; PLUS, wear that can occur on the internal SIDES of raw water pump ... as if the pump internal sides are severely worn the pump will not develop 'suction' as the leakage will be across the sides of the impeller vanes ----- although usually a slow process of the loss of pump efficiency. You'll need a micrometer and OEM spec. dimensions to do this. In a pinch, the impeller should be 'slightly larger' in width than the housing space it fits into.

Also check for previously lost/broken pump vanes that migrated 'downstream'.
 

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Another nasty, look for the little paper cap often found under the cap of the anti-freeze jugs used for winterizing. If you dump one of these caps into your bucket, and it is picked up, at some point the next season it may block a line.

I found this problem the hard way, and it was a marine mechanic who did the winterizing...
 

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Discussion Starter · #12 ·
Hi to all, got into the "no water", thing, a friend came down and we started "flushing/ back flushing", ended up pulling the exhaust off, all stopped up, and cleaning it out. Working great now, but a 'new' exhaust elbow is in order. Thank to all of you for your input in fixing this, it saved the 'sailing' season!
 
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