2QM20 Engine Integral Cooling Water Pump Replace/Repair

[rardiH36]

Has anyone with a 2QM20 engine replaced or rebuilt the engine integral cooling water pump?

Mine has begun to "weep" some fluid through the weep-hole.

I do have the official Yanmar QM series manual. In section 7.2, the manual has an exploded drawing/schematics of the pump parts. The pump can easily be removed from the front of the engine block. Then it seems the pump can then be disassembled rather easily without much in the way of special tools. One part shown is a "water seal ring".

I do have a local Yanmar dealer, only 300 yards away, to query. But before I go about the repair, or maybe have the Yanmar dealer do it, I thought to ask if anyone on the forum has prior experience = "things to know".

Another aspect: Whilst the original design for my engine gave the integral pump raw the seawater duty, Hunter had modified cooling system on this engine so that this pump instead circulates the contained anti-freeze circuit. Hence the pump has not been subject to saltwater corrosion. Probably why it has taken 37 years to begin acting up!

 

[Johnb]

I have sent you a private message.

 

[Ed Schenck]

Can't help. My 2QM20 was identical to yours. But that pump never failed. I did have to rebuild the sea water pump though.

 

[jssailem]

Not a Yanmar engine user, but most "freshwater cooling" systems are similar. You cycle water/coolant from a tank through the engine, through a heat exchanger, maybe through a hot water heater and back to the tank. The "fresh water pump" is driven by the engine (most often a belt that wraps around a pulley running from the crankshaft to the alternator and to the water pump). The water pump has a weep hole. When you see mist/water/coolant coming from the front of the water pump, it is time for a service. Failure to address this means you will eventually get a failure of the pump and an overheat of the engine.

1. Drain the coolant.
   
2. Remove any cover, the belt,
   
3. unbolt the pump.
   
4. Check for wobble of the shaft/grinding of the bearings, failure of the seals... Replace parts needed - OR just get a new pump. They are not expensive and 37 years of service is a "call it Good" thing for me.
   
5. Clean the face of the engine block, Apply a sealant/gasket.
6. Install new or refurbished pump.
7. Drink a beer while sealant sets...
   
8. return belts to operating position, refit any other covers.
   
9. Fill tank with coolant and burp the system... I had a friend stand on the gunnel, hold the standing rigging and rock the boat to burp the air.. Worked great. A few passers by commented "What the ...." - Just burping the engine....
   
10. Start the engine. Check for leaks and temperature. Correct if they appear. Top off the coolant tank.

Another beer and go sailing...Run engine up to WOT checking for leaks and temps.
A 2 hour job. Smile when the engine temps are on the mark.

 

[rardiH36]

Not a Yanmar engine user, but most "freshwater cooling" systems are similar. You cycle water/coolant from a tank through the engine, through a heat exchanger, maybe through a hot water heater and back to the tank. The "fresh water pump" is driven by the engine (most often a belt that wraps around a pulley running from the crankshaft to the alternator and to the water pump). The water pump has a weep hole. When you see mist/water/coolant coming from the front of the water pump, it is time for a service. Failure to address this means you will eventually get a failure of the pump and an overheat of the engine.

1. Drain the coolant.
   
2. Remove any cover, the belt,
   
3. unbolt the pump.
   
4. Check for wobble of the shaft/grinding of the bearings, failure of the seals... Replace parts needed - OR just get a new pump. They are not expensive and 37 years of service is a "call it Good" thing for me.
   
5. Clean the face of the engine block, Apply a sealant/gasket.
6. Install new or refurbished pump.
7. Drink a beer while sealant sets...
   
8. return belts to operating position, refit any other covers.
   
9. Fill tank with coolant and burp the system... I had a friend stand on the gunnel, hold the standing rigging and rock the boat to burp the air.. Worked great. A few passers by commented "What the ...." - Just burping the engine....
   
10. Start the engine. Check for leaks and temperature. Correct if they appear. Top off the coolant tank.

Another beer and go sailing...Run engine up to WOT checking for leaks and temps.
A 2 hour job. Smile when the engine temps are on the mark.

jsSailem: Many thanks for your detailed reply. I will go at the pump repair (or replacement) quite soon. For some of the 2QM20's, like the one that I have, they were originaly designed for seawater through the engine block via the engine integral pump. Hunter modified the system so that the engine integral pump instead pumped around anti-freeze coolant through the engine block and through an external heat exchanger mounted on whatever convenient nearby bulkhead that was available and finally back through the engine. They added a second external belt driven pump to intake raw seawater, then through the external heat-exchanger, and push back out through the exhaust elbow. I bit ass-backwards compared to most set-ups. But it was successful method behind the madness!

 

[Alctel]

Hi Rardi

Yeah, I've had to do both of mine. Your seals are probably shot - I'd buy the seals/gaskets separately and do it yourself, way cheaper than getting a dealer to do it and not hard at all. This is the coolant one hey (originally raw water)? I actually had to do that one a few months ago, pics here;

http://www.gudgeonblog.ca/fixing-engine-coolant-pump-and-an-amazing-days-sailing/
Do you have the service manual? It has a writeup on how to do it, complete with diagrams

If it's the other one, I haven't done that one for a while.

 

[tmjb]

L
Hi Rardi,

As we've discussed before (you sent me info re the Sen-Dure remote cooling system - thanks again) like Ed I have the 2QM20 with the same set up re the remote freshwater cooling but in in the two seasons that I have had the boat thus far I have not had a problem with the integral engine cooling pump which, as you say, pumps coolant in out setup. The feedback you got, particularly the specifics from Alcatel, are great to have for the future re that pump and it would be good to hear your experience as you address yours.

I apologize if this hijacks this thread somewhat but I have a related question that this prompts me too ask regarding the add-on seawater pump that is part of the Sen-Dure system. The pump is driven by the belt that also drives the alternator and is bolted to a bracket that is in turn bolted to the engine. However, for simplicity, due to the geometry of the pump etc. it is mounted so that the cover that provides access to the impeller faces toward the engine and is therefore inaccessible other than by removing the pump. This is of course very inconvenient if the impeller gives out at a critical point (I speak from experience) since it requires removal and re-installation of the entire pump. I have been toying with the idea (some way down on my to do list right now) of devising a bracket that would enable the pump to be mounted the other way round such that the cover is accessible. Just wondering if anybody else has thought about and/or done anything regarding this.

 

[Ed Schenck]

Not sure that I follow. What is behind your sea water pump?

 

[tmjb]

Apologies for not being clear Ed. As in your picture the pulley for the 'add on' seawater pump (bottom right) is forward, the pump, and most importantly the cover for the impeller, faces aft, toward the engine itself. Hence to access the screws to replace the impeller you have to remove the pump.

Hope that clarifies.

 

[rardiH36]

Alctel:

Thanks so much for sending the link with your pump repair description and the good photos. I see your "circlip" removal tool in your photo. Good to know that removing the clip enables the pump to be disassembled. Yes, I have the 2QM20 manual with the same exploded view diagram as you have open on your pump repair "workbench" in the photo.

As to finding the needed parts, by your description, almost seems that these were available in your area from even a non-Yanmar dealer? Can you remember what parts you needed to effect the repair? Certainly a new pump/engine mating gasket would be useful. (But also I do have gasket paper and gasket compound to make my own if necessary.) And I expect the water seal ring for sure. Anything else? I am thinking that while I have the thing apart maybe new oil seals as well?

Again thanks.

 

[rardiH36]

L
Hi Rardi,

As we've discussed before (you sent me info re the Sen-Dure remote cooling system - thanks again) like Ed I have the 2QM20 with the same set up re the remote freshwater cooling but in in the two seasons that I have had the boat thus far I have not had a problem with the integral engine cooling pump which, as you say, pumps coolant in out setup. The feedback you got, particularly the specifics from Alcatel, are great to have for the future re that pump and it would be good to hear your experience as you address yours.

I apologize if this hijacks this thread somewhat but I have a related question that this prompts me too ask regarding the add-on seawater pump that is part of the Sen-Dure system. The pump is driven by the belt that also drives the alternator and is bolted to a bracket that is in turn bolted to the engine. However, for simplicity, due to the geometry of the pump etc. it is mounted so that the cover that provides access to the impeller faces toward the engine and is therefore inaccessible other than by removing the pump. This is of course very inconvenient if the impeller gives out at a critical point (I speak from experience) since it requires removal and re-installation of the entire pump. I have been toying with the idea (some way down on my to do list right now) of devising a bracket that would enable the pump to be mounted the other way round such that the cover is accessible. Just wondering if anybody else has thought about and/or done anything regarding this.

TMJB: Your question certainly is close enough to the topic of the thread to not even come close to any definition of "hijacking".

Failing to open the seawater cock one time (distracted from my normal routine by guests), I also destroyed my seawater pump impeller while on the water. Fortunately we had a gentle breeze. And one guest could handle the boat well enough to tack back and forth across the harbor while I got a replacement installed (which fortunately I had on hand.) I surprised myself. Only took about 15 minutes.

I also have contemplated turning around the external (to the engine) belt driven seawater pump. And I remember staring at the engine one day about it. The constriction to the modification is that if the pump is turned around 180 degrees, because the pump shaft pulley must still align with the crankshaft/alternator belt, then the pump body and the hose connections on the pump, would extend forward beyond the plane of the removable wood engine compartment cover which is behind the companionway stairs. I no longer remember by how many inches. But it was enough to dissuade me from doing anything about modifying the OEM setup. Decided that I just gotta live with it. Let me know though if you discover an workable solution!

 

[tmjb]

Rardi,

Thanks for your tolerance re my potential hijacking of the thread and your reply.

15 mins to change that impeller is very impressive. You must work very efficiently. When it happened to me I didn't even attempt to fix it while sailing (I was single handed). I sailed back to my mooring and dealt with it there. In the interim, and given that my current pump is not in the best shape, I found a new pump somewhat reasonably priced on ebay and once I have found an appropriately sized pulley I plan to install this and keep the other as a spare ready to install in lieu of an impeller change to speed things up.

I thought about the potential conflict between the reversed pump and the engine compartment panel but did not get around to checking into that in detail. As I said this is not my top priority. Hopefully I'll have time to investigate further one of these days and will certainly let you know if I find a good solution.

 

[kloudie1]

Nomenclature note: Yanmar calls the water seal an oil seal.. the "oil Seal" is what keeps the water inside the impeller case.. ya definitely want to change that.. The piece that Yanmar calls the "water seal ring" is a round rubber part that rides on and rotates with the shaft outboard of the "oil seal". Its job is to fling any water leaking through the seal off the shaft before it gets into the bearings. The flinger ring is usually re-usable.
The bearings are off-shelf items that are inexpensive.. and easy to replace. They should be purchased with seals (usually 2-RS) instead of open..

 

[Alctel]

Alctel:

Thanks so much for sending the link with your pump repair description and the good photos. I see your "circlip" removal tool in your photo. Good to know that removing the clip enables the pump to be disassembled. Yes, I have the 2QM20 manual with the same exploded view diagram as you have open on your pump repair "workbench" in the photo.

As to finding the needed parts, by your description, almost seems that these were available in your area from even a non-Yanmar dealer? Can you remember what parts you needed to effect the repair? Certainly a new pump/engine mating gasket would be useful. (But also I do have gasket paper and gasket compound to make my own if necessary.) And I expect the water seal ring for sure. Anything else? I am thinking that while I have the thing apart maybe new oil seals as well?

Again thanks.

I replaced two seals I think - the water seal ring and the oil seal. The gasket to connect to engine I think I made myself out of gasket paper I seem to remember. It's worth doing both while you have the thing apart.
I got my parts from a local Yanmar dealer, after looking up the part number of the seals. They seals were all bought separately but there is a rebuild kit they sell as well.

 

[Jim Legere]

Apologies for not being clear Ed. As in your picture the pulley for the 'add on' seawater pump (bottom right) is forward, the pump, and most importantly the cover for the impeller, faces aft, toward the engine itself. Hence to access the screws to replace the impeller you have to remove the pump.

Hope that clarifies.

While it is awkward, it is certainly possible to remove the cover of the salt water pump, replace the impeller, and re-install the cover with the pump mounted 'backwards' - I have done it. Working by feel or with a mirror is not ideal and it may be faster to remove the pump, as you suggest. I have thought about getting a Speedseal kit for that pump.

 

[tmjb]

I'm very impressed that you've changed the impeller with the pump in place Jim. Not something I think I'd attempt.

Thanks so much for the link to Speedseal. I had something like this for pumps on a rebuilt Atomic 4 which were great but had not heard of Speedseal before. Expensive but definitely something to consider.

 

[Ed Schenck]

Got it. Never did an impeller in that pump until I had to completely rebuild it one time. Forgot, was only considering the one on the engine.

 

[rardiH36]

Thanks all for the participation to the thread.

To update my status, the local Yanmar dealer had the repair parts in stock. That would be the two "oil" seals and the water ring. List and paid price for the three was $19.75. I put the oil seals in the "oil" category because of kloudie1's advice about the nomenclature. The oil seal on the engine side does the job of preventing the engine oil from migrating out. The "oil" seal on the impeller side does the job of preventing coolant water from migrating in which then would leak out through the pump's weep hole. The pump's bearings seemed to be in very good condition = no replacement.The pump shaft was not scored in any appreciable way. So I am expecting a good outcome.

Anyway, no real issue removing the pump from the engine. Then to reinstal the new. The pump shaft was not scored in any appreciable way. So I am expecting a good outcome.

I haven't installed the pump back on the engine yet. Will let the forum know if anything re portable is encountered.

The Yanmar dealer did look up the price for a complete new pump. $ 830!

 

[tmjb]

Sounds good Rardi. Thanks for sharing as always. Good luck re the outcome. Pls keep us posted.

 

[BrianRobin]

Some of these replacement prices for complete pumps are crazy. I got a price for one on my Perkins from a dealer in Mass., for an aftermarket pump, $1124.00, plus shipping. I got one from a Perkins dealer in the UK, with exchange, delivered to my door, was $113.50 and it was a Perkins original.