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Old 07-03-2015, 03:43   #1
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Yanmar raw water blocked! Help-semi urgent

Hello all,
Having tricky few days on the hard at the moment as my Yanmar 3GM30 (raw water) overheated on way to weekend slip job (going ok).
So it's Saturday night here and my S&S 34 goes back in on Monday. I'm hoping to get it running by then, eternal optimist by nature. I'm considering an acid flush as the blockage may not be total, raw water was running ok (but not as strong as should be) when I set off. However after 20mins overheated, no exhaust water coming through, shut down engine, sail to an empty mooring. Swap in new impeller, start motor, no raw water, shut off.
My S&S is used regularly up and down east coast Aus, and engine run at least every couple of weeks.
Apologies for long post but I know you knowledgable people need all the details to get into the thread and assist me.
So option 1, flush raw water system with acid wash or a product designed for the job and available on a Sunday. I've searched the forum about flushing, lots of great info, but what if system already blocked?
Option 2 remove jacket and elbow and soak in dilute acid solution.
Option 3 tear down motor!
Option 4 sail back to my mooring, easily done (and easily buggered up),
Most likely option.
Any help much appreciated, some day I'll be old and wise enough to reply to others threads, but much to learn beforehand,
Thanks, webbyj


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Old 07-03-2015, 03:58   #2
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Re: Yanmar raw water blocked! Help-semi urgent

Start at the sea cock, take off hose, open sea cock and see if water comes in. Yes, then it is not the sea cock. Reattach hose and move to next connection, repeat test. Continue till you reach impeller. Alternatively, start at impeller and work back to sea cock.
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Old 07-03-2015, 03:59   #3
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Re: Yanmar raw water blocked! Help-semi urgent

OK, have you done any of the following.
Checked that water is getting to the pump OK, I.e. is the seacock or strainer blocked.
Checked the exhaust mixing elbow is not blocked.
Taken out both water jacket annodes (zincs) on the block and checked condition of jacket at these points.
Confirmed pump is actually pumping.
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Old 07-03-2015, 05:37   #4
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Re: Yanmar raw water blocked! Help-semi urgent

+1.. I agree with last two posts.. the blockage is anywhere from the strainer under the boat to the strainer before the water pump.. probably a clump of barnacles in the strainer under the boat

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Old 07-03-2015, 05:57   #5
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Re: Yanmar raw water blocked! Help-semi urgent

Thanks for the replies.
I have checked strainer, seack, and water pump, all fine.
Haven't checked elbow, will remove along with anode first thing tmrw morning.
It may be useful to know that my system doesn't have a hose connection into the elbow. I assume the water flow is injected straight from the jacket.
Thanks for your help
Webby


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Old 07-03-2015, 07:38   #6
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Re: Yanmar raw water blocked! Help-semi urgent

Just out of curiosity...

Did your old impeller lose a few fins, and if so have you found them?
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Old 07-03-2015, 07:48   #7
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Re: Yanmar raw water blocked! Help-semi urgent

Ok, so I've taken the elbow off and was partially blocked but can be easily blown through.
So I double checked pump is working by taking impeller out and rotating pulley by hand, spindle turns fine.
I also disconnected the hose from the thermostat housing and pumped via an electric pump water through from the strainer past the pump and past the thermostat. All fine and plenty water flow. Took the stat out, blocked hose from bypass and pumped again, no water coming out of jacket injection into elbow.
So I'm thinking I take the jacket off next and then pump again to see if blockage is in block? Unsure of exact route raw water takes from stat to jacket. Any help much appreciated.
If this thread should be in engine section maybe someone could tell me how to move it.
Thanks webby


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Old 07-03-2015, 07:50   #8
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Re: Yanmar raw water blocked! Help-semi urgent

Re the impeller, no fins lost, was in good condition but fitted a new one anyway,
Thanks for your help,
Webby


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Old 07-03-2015, 08:54   #9
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Re: Yanmar raw water blocked! Help-semi urgent

I have a Yanmar 3HM35F that kept blowing seals on the raw water pump. Ultimately I found that the 90 degree elbow on top of and feeding the exhaust elbow had a carbon buildup the stopped the flow. I replaced the elbow with a straight fitting, but still checked it at each oil change. Problem no longer exists. I hope that may be of some help to you, if not to others who may experience the same problem.
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Old 07-03-2015, 11:35   #10
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Re: Yanmar raw water blocked! Help-semi urgent

Be cautious pumping water thru the system with electric pump & engine not running.You can force water back up the exhaust mixing elbow,thru open exhaust valve & into cylinder-thereby causing a waterlock & possible internal damage if you try to turn engine over.A water lock can be cleared by opening decompressor if equipped.
Safer method is to fill a bucket with water,stick the seacock hose into it,& start engine,so that RW pump is sucking from bucket.
Did you check exhaust hose thru muffler for blockage?
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Old 07-03-2015, 12:07   #11
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Re: Yanmar raw water blocked! Help-semi urgent

I also have a 3GM30, one year there was no water exiting transom after launch. checked all the above items that has been suggested and still no water. it ended up being an air lock in the pump suction hose, so now before launch I fill strainer to overfill and fill suction hose plus hose from strainer to pump. never have had a problem since.
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Old 07-03-2015, 15:12   #12
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Re: Yanmar raw water blocked! Help-semi urgent

Thanks for the replies. I have the elbow disconnected when pumping water through, so I was thinking I could watch for water getting to the elbow or not as it turns out. I think this should take away the possibility of water backing up in the exhaust and returning via the valves to the cylinders. Is this correct?
I've a bit if painting to do first then I'm thinking I take the jacket off to see if water pumps through block?
All your help much appreciated
Thanks, Webby


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Old 07-03-2015, 15:49   #13
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Re: Yanmar raw water blocked! Help-semi urgent

Hi iWeb try taking the feed hose off the water cooled exhaust manifold where it exits to the elbow clean out the outlet in the manifold itself. I have had problems here in the past !!! at the moment I have the exhaust manifold off my motor to replace it as it had rusted through against the head. when I removed the cover plate to expose the inside there was an amazing build up of gunk hardly enough room for water to pass through. To get going again twist a screw driver through here or wire until you get a good flow and I would suggest when you can remove the cover and clean this water passage out.

Yes my motor is the same raw water as yours ---- one last thought have you removed the thermostat housing and test the thermostats in a pan of boiling water ( I hope they open for you as they are $60-70 each) there is a small bye pass tube in here that runs from the inlet through to the bottom thermostat housing make sure this is clear. Good luck Jacko
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Old 07-03-2015, 16:16   #14
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Re: Yanmar raw water blocked! Help-semi urgent

Thanks Jacko, sounds like you've been here. I'll remove the jacket cover and take a look and see if I can carefully poke them clear.
Bootstripe done, one more antifoul, then get engine running, all part of the joys of cruising. I'm sure I'll learn a few lessons from this.
Cheers, webby


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Old 07-03-2015, 18:45   #15
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Re: Yanmar raw water blocked! Help-semi urgent

Get the tel# for "Complete Yacht Service" in Ft.Lauderdale, ask for Mark, the owner ( USMC) tell him Pat N, formerly from there now in Tampa told U to call.
He is the Yanmar dealer there and knows everything there is to know about Yanmars.
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