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Discussion Starter #1
I just rebuilt the raw water pump on my Yanmar 2GM20. The pump worked fine when I took the boat out, I probably motored about 30 minutes. Went for a sail, and when I fired the motor up to come back, no water was coming out of the exhaust. I took off the raw water strainer top, ran the motor, and still no dice. I ended up disconnecting the water hose where the pump supplies water to the motor and the pump was then able to supply water again. I motored back without any problem. I assume there must have been an air blockage somewhere in the line (probably at the impeller?). If so, how would it develop after initially running for half an hour? If not, what might have caused it. Is my method the best way to fix the problem should it happen again?
 

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some people lube the heck out the impeller when they change it to help it prime. i have heard of some using lithium grease and some Vaseline. i dont know if anything is wrong with either some body else will know for sure.

also you might have just picked a trash bag they fell away when you shut it down to check it out
 

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Both of my raw water strainers work on a suction principle. The are mounted above the water line. With the top off, they would not work at all. Once the water already in the strainer drained out, the engine would be dry.

Is yours mounted below the waterline?

If you ran the engine for an extended time without water in the pump, you probably damaged the impeller. The instructor of the engine course I took at Mack Boring recommended coating new impellers with olive oil. This makes them easier to install and keeps them lubed during the initial startup while the pump is dry.
 

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Discussion Starter #4
Both of my raw water strainers work on a suction principle. The are mounted above the water line. With the top off, they would not work at all. Once the water already in the strainer drained out, the engine would be dry.
Is yours mounted below the waterline?.
Yes it is. In fact, when I do it, I have to control the flow with the intake valve. A while back the same thing happened and someone suggested taking the top off and it worked. Not sure why, but I think it reduces the surface tension in the rest of the line. Doesn't really make sense to me because I would think the water pressure from the intake would offset any surface tension. Anyway, it didn't work this time!
 

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Discussion Starter #5
Still having the problem! The boat sat for a week after the last episode. Motored out, no problem. Went for a sail, and started the motor to come back in.... no water! Same solution. Seems like heeling while sailing must have something to do with it. But that makes no sense to me. The only thing I changed (other than the rebuilt pump) was the 1/2" hose that goes from the pump to the motor. Bought it from an auto parts store, but It's cooling hose and seemed Identical to the hose that came off. Any ideas?
 

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Sounds like the pump may be losing its prime. Most likely cause is wear in the pump that has opened up the clearances and prevent the impeller from sealing correctly and drawing water in from the suction line. Check for scoring in the cover plate. If its scored, either file it smooth or replace it. An air leak in the suction line could also be part of the problem.
 

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ok ive had this problem recently,after sailing u probably have heeled the boat quite a bit & in doing so dumped out all the water in exahust line from the water lift back....it takes a few minites to fill up again !! try pullins off the sea water line going into the exhaust if there is water there than just wait a minite or so till water apears at stern[after re connecting line]
 

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I too suspect the pump. An impeller pump is designed to be self priming. If it won't pull the air out of the hose, something is wrong with it, or you have an air leak in the system.

You did not have the problem with the boat sitting a week, so an air leak is unlikely. I would focus on the pump. Many people carry a spare anyway so they can change it out and rebuilt the spare pump later.
 

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Discussion Starter #9
ok ive had this problem recently,after sailing u probably have heeled the boat quite a bit & in doing so dumped out all the water in exhaust line from the water lift back....it takes a few minutes to fill up again !! try pullins off the sea water line going into the exhaust if there is water there than just wait a minute or so till water appears at stern[after re connecting line]
Interesting. So, this would mean that the boat has always done it, but that I've become aware of it now, because I've rebuilt the pump. Classic mechanics syndrome, where a mechanic fixes one thing, and the vehicle owner suddenly becomes hyper sensitive about things that have gone on for years. Drives my brother (a mechanic) crazy!:laugher Come to think of it, I'll usually check for flow at the dock, but seldom when I'm out, so this makes sense. I don't think the pump is the problem, as it is rebuilt (including a new shaft), and draws strongly when I go out and when I flush the system at the dock. I'll test the theory and report back. Hopefully, I won't report that I don't have the problem anymore because I have a new engine:eek: !
Thanks!
 

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Discussion Starter #10
ok ive had this problem recently,after sailing u probably have heeled the boat quite a bit & in doing so dumped out all the water in exhaust line from the water lift back....it takes a few minutes to fill up again !! try pullins off the sea water line going into the exhaust if there is water there than just wait a minite or so till water apears at stern[after re connecting line]
You are right! The engine on my Yankee 30 is midships, so the exhaust water has to travel over half the length of the boat, to exit. After the water in the exhaust line has drained by the heeling of the boat, it takes about 2 minutes to get to the Stearn. When you've just rebuilt the water pump and are sensitive to cooling issues, that seems like an eternity! All is well, thanks for the insight!
 

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I get this problem when I sailed for long period on port tack at >40deg heel. apparently the water intake ocassionally is out of water and water drains out causing air trap. filling up the pump discharge hose solve the problem each time.
 

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Discussion Starter #12 (Edited)
I get this problem when I sailed for long period on port tack at >40deg heel. apparently the water intake ocassionally is out of water and water drains out causing air trap. filling up the pump discharge hose solve the problem each time.
Why would you be sailing for long periods at 40 degrees? Think it's probably time to reduce sail. You might actually move forward as opposed to sideways:laugher Generally, I think anything much over 20 degrees is excessive. Hard on the boat, sailors and counter productive. Anyway, I certainly didn't have the intake out of the water
 

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Why would you be sailing for long periods at 40 degrees? Think it's probably time to reduce sail. You might actually move forward as opposed to sideways:laugher Generally, I think anything much over 20 degrees is excessive. Hard on the boat, sailors and counter productive. Anyway, I certainly didn't have the intake out of the water
well, its not often we get such a breeze here so we kinda enjoy it. we hardly even reef our sails here too. just let it out if wind gets too strong. anything more 25kts is probably couple times per year only. :D
 

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Did you use a new (or the old) paper gasket t oseal the cover on the pump.
If so, take it off, and try a bit of RTV silicone sealant (auto parts store). You want only a little sealant, as too much ( or a buildup of old paper gaskets, etc) will cause the cover to sit too far from the impeller, and it won't pull as much water.

Did you reuse the old cover? Was it scored?? If so, clean the other sit and flip it over.
I used to have the exact some trouble as you. Had to close the engine seacock while sailing, to prevent water from running out / air pulling in (maybe from the exhaust). Turned over scored cover to other side, and it;s been perfect.

You could also have an airleak in the new hose / clamps.
Sailing / water rushing past hull will cause (venturi effect, I believe) the water in the through hull and hoses to ne "pulled" out, if it can be replaced ny air squeezing by the pump / cover plate, oe anothre source (airleak in hoses)
 

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Discussion Starter #15 (Edited)
QUOTE=rikhall]Hey
OK - similar problem I have. New to us boat - a 1980 Irwin Citation 34
Motors perfectly - always starts, always spits water.
Twice - sailed and then when starting the engine hot light soon came on and no water was coming out.Both times, took the hose off, looked at the impeller - everything seemed fine.Let it cool - started it up and everything was fine.
Uggg! If you come up with a solution - let me know.
Rik

Hi Rik:
If you look back at the post, I found the problem was me! However someone responded who heeled over so far it exposed his intake and allowed air in (though, someone else stated the pumps are self priming) On some boats big seas might also do it . If air is getting in your intake, I think opening the line at the impeller (as you did) would allow the air to bleed out (but then, I'm no mechanic!). If this was the cause, closing the intake while sailing would cure it. BTW, whenever I close the intake valve, I always put the keys near the valve, so I have to go there (and open the valve) before starting the engine. Many others probably know this trick, but everyone I've shown it to is impressed (as was I when someone showed it to me). If you respond, please do so in the thread, as I will get it, and others will benefit as well. In fact, I will post this email. Hope thats ok.
Thanks, Bill[
 

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I moved my raw water strainer about a foot lower and so far she has started fine both times we have been sailing. But - light winds and only 5 to 10 deg heel. We will see what 15 - 20 degs does.

I too have learned that boats are built to an optimum heel for optimum speed. Our Tanzer 28 sailed fastest at 15- 20, over 20 we lost a lot of speed and went "sideways" more

Have not figured out the IC24 yet.

Rik

Rik
 

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Discussion Starter #17
I moved my raw water strainer about a foot lower and so far she has started fine both times we have been sailing. But - light winds and only 5 to 10 deg heel. We will see what 15 - 20 degs does.
Rik
Rik
Just curious, what is the theory on moving the strainer down? I assume to get it below the water line on all points of sail? Seems to me that if it was full going out, it should stay full unless the intake is exposed to air.
 

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Just curious, what is the theory on moving the strainer down? I assume to get it below the water line on all points of sail? Seems to me that if it was full going out, it should stay full unless the intake is exposed to air.
Like I said - I am not sure the problem is fixed - just reporting what happened. If and when I really find out what caused the three "no water after sailing" happenings - I will let you all know. For now - it is try one thing at a time and see the results.

Rik
 

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Maybe you could install a tee in the line with a valve open to atmosphere so you could open it after sailing to burp out any trapped air.Had the same problem with an airconditioning pump on a Norseman 447.We just pulled the water line off to let the air out.A tee and a ball valve would be quicker.

Phil
 

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Discussion Starter #20 (Edited)
Maybe you could install a tee in the line with a valve open to atmosphere so you could open it after sailing to burp out any trapped air.Had the same problem with an airconditioning pump on a Norseman 447.We just pulled the water line off to let the air out.A tee and a ball valve would be quicker.

Phil
Where was the air coming from? It seems to me that if you have air in the system you've either got a leak (doesn't make sense in Rik's case), or you are draining water and taking on air in the intake while heeling. I'm betting that when Rik sails in some real wind the problem will occur again. I would shut the intake valve before heeling. If it doesn't occur...problem solved. If it does, I never claimed to be a mechanic :p It's hard to believe they would place an intake where it would be exposed to air in anything less than a knock down, but apparently they do. My intake is about a foot from my keel. If it sees daylight, I'm on my side!
 
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