2GM20F - Fresh Water Circulating pump - SailNet Community
 
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post #1 of 6 Old 06-04-2006 Thread Starter
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Question 2GM20F - Fresh Water Circulating pump

Hi,

I need some information about the fresh water-circulating pump on a Yanmar 2GM20F.

Last weekend while mooring my IP-27, the engine had a C W Indicator/horn came on and I shut it down within 5 seconds. Opening the cockpit engine compartment hatch a strong odor of an overheated engine and coolant greeted me.

The engine had been running about 15 minutes at the dock before the short trip to the mooring. When the engine cooled, I checked the coolant level, there was none to be seen in the heat exchanger. It was late, I shut everything down and I did not pursue the issue till today.

This morning I went out to the boat and added about a quart of distilled water which brought the coolant level back to normal. I checked the engine oil level which was fine.

The engine was started without difficulty and I ran it for 2-3 minutes and then shut it down. Rechecking the coolant level showed a small decrease in levels and a bit more water added.

On the second start it ran but there was an intermittent noise from the front of the engine and I shut it down once more. Again I checked the coolant level and added a small bit more water when it had cooled off.

The third time I started the engine, there was a persistent noise from the front end. I saw the pulley wobble for an instant and then there was a high pressure stream of water/coolant/and some brown 'liquid stuff' spray the area of the fresh water pump and even reach out of the engine compartment onto the cockpit seats. Again I shut it down, checked the coolant and added a tad more water.

All belts were checked and found to be tensioned correctly. The raw water pump was functioning normally and putting out it's usual volume of water which varied with the throttle setting. All hoses were also checked and found to be OK (If it had been a hose malfunction, there would not have been the loud noise from the engine.)

From what I have seen and heard from the engine, I feel it is the fresh water-circulating pump not functioning.

My question is in several parts:

1) What tests can I run to make sure that the issue is the FW pump?

2) How difficult is it to take it off and put it back on? (The access, unlike most of the rest of the engine, is very good.)

3) Once it is off the engine are there things I can check and possibly replace parts or should I just bite the bullet and get a whole new pump. (I do not have the shop manual for the engine but plan on getting one during the week).

Since this is a very popular engine series (original engine on my 1985 ip-27 # 41) I was hoping there is a lot of background information available from our members.

That’s the story, folks. Any offerings will be greatly appreciated.

Thanks to the Group in advance,

Bill R on Sun Dancer
Oceanport NJ
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post #2 of 6 Old 06-05-2006
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Infrared temp gun

One of the best trouble shooting tools for cooling systems is the point and shoot temp guns. Price has dropped in the last few years and they are avail now for under $50. Max temp on cheap guns is only 400 to 500 degrees but that covers most mere mortals trouble shooting tasks.

You can slid the laser dot down the hoses and across the engine block and see what is heating up and what is not. For instance you can watch a thermostat open by seeing the output side of the housing DROP in temp almost instantly when the thermostat opens.

For your specific issue I can't say exactly how you would trouble shoot except to point out "it's all about temp// what temp where and when". I assume you are going to pull the cover plate and check the impeller of the suspect pump. Need to account for all the bits and pieces if the impeller has self destructed. It does not take much in the way of trash/odd bits to block flow and cause wierd overheat mysteries. If that happens you disconnect engine hoses and use shoreside water hose for backflush. It is best when doing that to have one of the little plastic strainers to run the outflow of the flush through to see what comes out otherwise you do a lot of work and are not sure it anything happened.
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post #3 of 6 Old 06-05-2006
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Infrared temp gun

One of the best trouble shooting tools for cooling systems is the point and shoot temp guns. Price has dropped in the last few years and they are avail now for under $50.

You can slid the laser dot down the hoses and across the engine block and see what is heating up and what is not. For instance you can watch a thermostat open by seeing the output side of the housing DROP in temp almost instantly when the thermostat opens.

For your specific issue I can't say exactly how you would trouble shoot except to point out "it's all about temp// what temp where and when". I assume you have are are going to pull the cover plate and check the impeller of the suspect pump. Need to account for all the bits and pieces if the impeller has self distructed. It does not take much in the way of trash/odd bits to block flow and cause wierd overheat mysteries. If that happens you disconnect engine hoses and use shoreside water hose for backflush. It is best when doing that to have one of the little plastic strainers to run the outflow of the flush through to see what comes out otherwise you do a lot of work and are not sure it anything happened.
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post #4 of 6 Old 07-12-2006
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I would also look at the coolant to try to determine if there is any oil in it - which would indicate a much bigger problem. If you find that you need a new impeller, the old one is often difficult to remove. There is a special "Impeller Puller" that helps. You can buy and entire service kit for the pump that should have all of the parts you would need. The are available at you Yanmar dealer. It is also recommended to pull the impeller with the pump still on the engine.

Check out the info on the IPPHOTOS.com website. This is a great resource for help. Here is the web address for details on your pump: http://www.ipphotos.com/view_ad.asp?...Cat2%5FID%3D29
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post #5 of 6 Old 09-16-2007
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Fresh water cooling pump

I had to replace the entire unit. The pulley wheel wobbled and leaked water also. Easy job. Be sure and also order a replacement gasket. For some reason they dont include it with the new pump. If you have a water heatet conected to the pump you will have to remove the intake ports and output ports from the old pump and install them on the new pump. The replacement pump comes with plugs in these openings.
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post #6 of 6 Old 09-17-2007
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The noise sounds like it might be the bearings in your fresh water pump.
I have a similar Yanmar built in 83 and I purchased a water pump kit this past spring and it fixed it up very nicely. First are you getting adequate water flow out your coooling water? The fresh water pump just pumps through the heat exchanger and then out through the water muffler and then outboard. This will not explain your loss of coolant in the main engine ciculating system. That is driven by a small pump that I believe has a metal impellor and rarely needs any work. You could also have a leak in the exchanger.


The water pump is easy to remove for inspection, just disconnect the hoses and then I think it was a 10 MM socket to take out the two bolts holding it in place. Surprisingly mine came out easily. I did put fresh thread lubricant on them before putting them back.

I ordered the kit from a Yanmar dealer and it was not that much. If you do get it the two bearing are on the shaft behind the pump it's self and there is a small circlip between them that is hard to see. Took some head scracthing until I found it.

Good Luck
Gary

Last edited by Gary M; 09-17-2007 at 12:57 PM.
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