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timmfive
22-08-11, 14:41
Keywords / Title:
Yanmar 3GM30 raw water cooled (RWC) Johnson pump raw water pump failing to reprime, causing engine to overheat.

We had this intermittent problem for almost 1 year.
What follows is my trials and errors, and ultimately a solution to this issue.
I am hoping this will help others out there as there seem to be alot of threads outlining the same/similar issue... but no solution found.


Problem:
- Engine overheating in rough seas, confused seas, and sometimes with steep following seas.
- Due to above circumstances, the engine would often overheat when approaching land, or when the wind died completely but left some sea state behind. Either scenario is the worst time to not have your engine!
- Explained the circumstances that caused the overheating to previous owner. He never had the issue in 13 years of running the engine.
- Also, we didn't have the issue during the first 6 months of having the boat.
- So issue must be new, or I must have introduced it during maintenance in some way.
- Quickest way to resolve issue was to undo supply hose on the intake side of the pump, let air/water drain out into bilge until solid column of water, reattach, start engine, let cool. Continue for another 15-20 minutes or so... hope... :(


Engine / pump specs:
- Yanmar 3GM30 raw water cooled. 13 years old. (Would estimate ~4000 hours?)
- Pump is a Johnson Pump F4B-902, 10-24509-02. Impeller Johnson 810B.


Actions taken:
1) Rebuilt pump completely. Same issue.
2) Threw a few new impellers at it: same issue.
3) Systematically ruled out backplate, paper gasket, intake filter, hoses, air leaks, back pressure, exhaust manifold/gooseneck etc.
4) This year, we replaced black intake hose with clear one to observe water/air flow.
Naturally on heel angles above 20 degrees, air would accumulate quickly and pump wouldn't reprime.
However, even on on 5-10 degree angles but with steep seas, small bubbles from the breaking seas would slowly accumulate. Eventually they would reach a stage where the pump would fail to reprime.

So with the clear hose I was able to observe the issue... why was it happening? Why can't the pump reprime? Why doesn't it just suck through the air bubbles as it goes along?

5) Experimented with different routes of the intake hose: far below waterline as possible, "S" shapes, loops, etc.
Regardless of intake hose position, air would accumulate.

6) Tried replacing the 3/4" (19mm) intake hose to 1/2" (~12mm). Idea was the thinner hose would introduce more suction. No joy.
(Interestingly, both diameters would empty a bucket of water in exactly the same amount of time!)
Even putting finger on end of intake hose... just doesn't seem to be enough suction in my opinion...



Solution:
- Went to Yanmar distributor with old pump in hand and a pair of calibers to measure inner chamber diameter, as well as Cam size.
- Didn't need calipers to see the cam size on new pump was 2 to 3 times thicker than original pump! :)
- Yanmar agent insisted the pump I had was the one for the fresh water (3GM30F) model and that the 3GM30 raw water pump is a smaller one he showed me.
- However, smaller Yanmar branded pump was ~€500. And exact "like for like" replacement of my bigger Johnson pump was "only" ~€220.
- So a bit of a surprise/confusion, but was reluctant to pay twice as much for a smaller pump.
- Was more logical to get the same pump that had worked fine for 13 years.
- The main thing was seeing the Cam size in the new pump. I will attach pictures.
- Note: the cam in both pumps are not replaceable... (else I would have fixed this last year!!!)

New Johnson pump specs compared to old pump:
- Yanmar p/n 128397-42500

Old Pump: Johnson Pump F4B-902, 10-24509-02. Impeller Johnson 810B.
New Pump: Johnson Pump F4B-903, 10-24509-01. Impeller Johnson 810B-1. (no paper gasket)

Old pump Inner chamber diameter: 50.2 mm. Diameter to cam: 48.25 mm.
New pump Inner chamber diameter: 50.0 mm. Diameter to cam: 46.00 mm.

Old pump moved ~180L/h at 1000 rpm.
New pump moved ~420L/h at 1000 rpm.
New pump moved ~630L/h at 2000 rpm.

(Yanmar manual says it should move ~700L/h.. but doesn't state rpm... and i'm not sure if this is in reference to the smaller Yanmar pump that I "should have", or the one that I Do Have...).
New pump had a noticable, considerable more amount of suction when putting finger on end of intake hose.
So much suction, that I was almost afraid my finger would get stuck on end of hose and I would have to kill engine.
Whereas, with the old pump, the suction was feeble and there was easy to plug hose and unplug hose with finger/palm.

Another test, was with intake hose full with a column of water, holding the intake hose vertically:
Old pump the water would be seen to work its way down thru the pump a slow, but considerable pace.
New pump the water would still work its way down... but very very slowly in comparison.

And *ULTIMATELY*... the new pump would prime anything...
ie: take a dry hose, dip it into a bucket of water, and it would suck the water thru the length of hose.
You could introduce air, etc, at anytime, and it would quickly fly thru the hose, thru the pump and thru the system.

:)

No problems since and we've been in some rough seas, steep seas confused seas, etc. (Aegean Meltemi)
All conditions where before we would wince and wait for the untimely <<bbeeeeeeeppp>> of the engine overheat alarm.
It has take awhile for us to gain trust in the engine in such conditions, but now we have regained confidence. :-)
Any bubbles from breaking seas just get sucked thru. The water coming out of the exhaust is noticably more in volume and power.
I have read that the max heel angle to run the Yanmar is ~15 degrees.
We don't motor when sailing on a steep heel angle.
Just motor when we need to get into a port, or if the wind dies.


Root cause:
- Previous owner took the boat up to the UK thru the French Canals. Had no problems.
- We had no problems in UK, English Channel, North France, etc.
- We took the boat back down to the Med thru the French Canals. Had no problems until once were in the Med.
- (In hindsight!) Reason why the pump cam was worn so much, so quickly:
a) 13 years old...
b) the silty, sandy water in the canals increased wear on cam.
(If the pump is rotating at ~2500 rpm, multiplied by 6 impeller vanes hitting the cam = ~15000 laps of the cam a

minute = 250 laps / second. introducing sandy/silty water makes a quick job of sanding down the cam with rubber vanes)

- - -
Conclusions...

Researched this problem for a solution on the internet.
(Google "yanmar 3gm30 johnson pump" for example.)
Found over 30 threads on dozens of sites that highlighted similar/same issue, but no solutions posted! :( The original poster would disappear, or get sick of people telling them to change the impeller. ;)
I will try and go back to all the threads I found over the past year and point them to this post in case it helps anyone out there.
Least I can do. It was a very frustrating issue as it was so intermittent and hard to repeat.
The conditions that caused the issue weren't condusive to troubleshooting... it was more.. get it working, get to port safe, etc.
Sounds simple now in hindsight... but at the time was hard to pinpoint. The clear hose really helped me understand the issue. Very cheap step in the troubleshooting process. Some of the forums did hint and replacing the pump, but quoted the pump at being €500. The reason I didn't do this sooner was that €500 was a very big expense for us, especially as a troubleshooting step, with no guarantee of resolve.

In conclusion... the pump is easy to take off and take to Yanmar and do a comparison with new pump. Shame the cam isn't replacable as on some pumps. Hopefully the measurements above will help someone out there too.

(See attachment of old + new pump side by side... the picture is worth 1000 words).

pvb
22-08-11, 14:51
Glad you solved your problem! In fairness, I think many experienced engineers might have spotted that the cam in your old pump was incredibly worn.

timmfive
22-08-11, 14:57
yeah, in hindsight, paying a call out charge for an experience yanmar engineer to have a look might have done it.
just thought i'd contribute to the forums in hopes of helping others.

currently going thru all the other threads with similar issue and adding this thread to possibly help others.

Halo
22-08-11, 15:05
What a great posting!!

If this is the same as the problems on some 3YM30's then you will have answered some more intermittent overheating problems!!

Thanks a lot for the insight

Martin

timmfive
22-08-11, 15:33
Cheers Martin,
Forgot to say in above post that I also ruled out Thermostat, and electric temp sender...
A bit OTT maybe, but it really was a tricky intermittent issue to troubleshoot.
I'm hoping all the measurements in the post will help others going forward.
It's the least I could do... as I am personally very happy that the issue is finally resolved! ... it was starting to become more frequent and a real concern for us.

I have updated a few posts on CruiserForums and other forums also.
Trying to update some on SailNet... was able to register, but now it seems their site/forums are down! Will try later...

nigel1
22-08-11, 15:51
Shame that the cam is not a serviceable item, which it tends to be on most Jabsco pumps.

timmfive
22-08-11, 15:56
yeah, I think some of the Johnson and/or Yanmar pumps have servicable cams, but not the one I have quoted above. :(
I remember asking a Yanmar distributor how much a complete pump was when we first bought the boat and was quoted circa €500, so naturally it wasn't an obvious option for a spare part.
However, the above pump quoted was "only" €220, which I think is not too bad considering all the individual spares inside, coverplate, impeller, bearings, etc would quickly add up to a few hundred.

I am keeping our old pump with worn cam in case our boat ever wends it's way up the canals again. The old pump works fine in calm-ish waters. And the canals are flat calm.

savageseadog
27-08-11, 08:30
yeah, I think some of the Johnson and/or Yanmar pumps have servicable cams, but not the one I have quoted above. :(
I remember asking a Yanmar distributor how much a complete pump was when we first bought the boat and was quoted circa €500, so naturally it wasn't an obvious option for a spare part.
However, the above pump quoted was "only" €220, which I think is not too bad considering all the individual spares inside, coverplate, impeller, bearings, etc would quickly add up to a few hundred.

I am keeping our old pump with worn cam in case our boat ever wends it's way up the canals again. The old pump works fine in calm-ish waters. And the canals are flat calm.

I posted the following on your last thread - has a useful link for parts breakdown and numbers for the pump so you can type into asap and get genuine johnson spares at a fraction of the price of the yanmar dealer re badged.

Are you sure the difference in the lobe size is not due to the fact that one pump is for the F version the other raw? There are two versions of the pump exactly the same bar that lobe?

---- my old post....---

The yanmar GM's with the Johnson pumps are YEU engines the last of the GM range before the model change (European manufacture) if you buy a standard impeller replacement they are wrong. Also the impellers come in two varieties half inch shaft (12.7mm) and 12mm shaft also there are slight differences between the YEU - GM Freshwater cooled and raw water cooled pumps.

The good news is that the Johnson raw water pumps are only £180 brand new from the dealer (marine power, et al.) as opposed to the jabsco at £300/400, or for new bearings and seals are less than £10! - i have the bearing numbers if you need them, we have a 3GM30FC-YEU (you can tell if yours is the YEU by looking for an E on the engine plate near the number.

Some people replace a Jabsco pump with the Johnson pump as there less than half the price as a replacement (though the dealers don't tell you this!). There is no difference in the mounting so you can get Johnson pumps on the older GM' engines.

The Johnson pumps also have the o-ring seal, far superior to the paper gasket. Make sure your oring is properly seated.

Datasheet and diagram for the Johnson Waterpumps for the GM raw and Fresh YEU ENGINES ---- >>
http://www.depcopump.com/datasheets/johnson/10-24509-01.pdf

vyv_cox
27-08-11, 08:36
The yanmar GM's with the Johnson pumps are YEU engines the last of the GM range before the model change (European manufacture) if you buy a standard impeller replacement they are wrong. Also the impellers come in two varieties half inch shaft (12.7mm) and 12mm shaft also there are slight differences between the YEU - GM Freshwater cooled and raw water cooled pumps.


I was caught out by that one. Took a new face plate all the way to Greece, only to find that it didn't fit. My engine is a YEU version, apparently those engines all arrived in Holland fully assembled except for the water pump, which entitled them to save import duty as the engines were being 'assembled' in Europe.

Slipperman
27-08-11, 10:36
Thanks for an interesting thread. I have a Yanmar 3YM 30, freshwater cooled. Thought about carrying a spare raw water pump, but put off by the Yanmar price. Can anyone tell me which Johnson equivalent I might be able to buy, and where?

ParaHandy
27-08-11, 21:53
Identical engine except that the impeller is secured with a keyway and the pump cover has a gasket seal. Your engine might be younger than mine? I had the same problem 5 or 6 years ago. The impellers were made undersize by 0.20" on the flank and 0.040" on the OD. Complained to Barrus with all of the relevant detail, flow rates Vs flank width etc and got nowhere. I had changed the impeller each year and kept the old ones so I had plenty of examples.

Barrus couldn't (or wouldn't) give me the correct size with tolerance; they thought a press run by Johnson just chucked them out to any old size ...

I replaced the cam (which was not really worn but seemed worth doing) and reversed the pump lid. The lid was quite deeply worn. I think that the one thing that will cause a failure is an excessive gap between the impeller flank and the housing.

Touch wood, no further problems but I wouldn't trust them as far as etc etc !!

FullCircle
27-08-11, 22:10
Thanks for an interesting thread. I have a Yanmar 3YM 30, freshwater cooled. Thought about carrying a spare raw water pump, but put off by the Yanmar price. Can anyone tell me which Johnson equivalent I might be able to buy, and where?

Get it in bits from Aquafax Luton

F4B-903
10-13337-01
which is fitted to the 3YM30. You will need this number when phoning



Impeller & Cover gasket 09-810B-1 £20.51

Bearing Front 05-08-124 £6.28

Bearing Rear 05-08-130 £9.80

Seal 05-29-139 £3.59 2 required

Shaft 01-46541 £38.00

all plus VAT

timmfive
28-08-11, 09:55
Are you sure the difference in the lobe size is not due to the fact that one pump is for the F version the other raw? There are two versions of the pump exactly the same bar that lobe?


Thanks for the info you supplied and the .pdf is helpful too.
I checked the plate on the engine. There is no "E" next to engine number.
It just says:
Model: 3GM30
Engine number: 19518
I reckon it could be one of the early ones?

The two pumps that Yanmar showed me (the smaller/expensive one, and the bigger/cheaper one) were very very noticable differences. I should have taken a picture and got the part number of the smaller pump. But it was wayyyy smaller just to look at. Not in terms of millimeters, but in terms of cm. He claimed the smaller pump was for the raw water cooled, and the bigger (Johnson) pump was for the Fresh water cooled.

The previous owner who had the engine fitted did not alter the pump in anyway. So I just stuck with the Johnson pump as desrcribed in my original post.

I can't be 100% certain as there is a myriad of part numbers and different manufacturers etc. But in my case, the two pumps appear to be identical when comparing side by side (despite the slight model number difference).
I am pretty confident that the lob/cam size on the old pump is smaller due to wear and tear and age. (As per the picture attached to my original post).

Hope this helps/answers your question?
Thanks again for the .pdf and info.

snowleopard
28-08-11, 10:48
A couple of points about the pumps on these engines. The fresh water cooled version needs a higher capacity raw water pump as it needs a greater flow to operate the heat exchanger.

On the raw water cooled engines there are two types of pump, one with a removable cam and a paper gasket under the cover and the other with integral cam and O ring seal.

It is important to check the bearings are sound as they will eventually wobble enough to let a lot of water out of the shaft seal resulting in water spraying on the alternator and killing it. I had to change the bearings on both of mine at around 1600 hours.

affinite
28-08-11, 18:58
I have a raw water cooled 3gm30 but havent experienced your problem. Mine actualy has a fairly new pump as it was replaced after failure a couple of years ago, but you now have me wondering if I should fit a raw water filter (I have one of those Vetus jobs somewhere) to prevent it happening. Do you think it would be a goor preventative measure ? or would the filter restrict the inlet and maybee even bring on the wear problem ?

timmfive
29-08-11, 09:07
Affinite,
I'm sure some of these more experienced people will agree that a raw water filter would be very recommended. It will keep any big/visible objects out of the pump and moreover out of the engine cooling paths.
None of the raw water strainers are fine enough to filter silt or sand really.
But unless you are in a particulary silty/sandy place, like the canals, you needn't worry about the issue if you pump has been replaced recently.

But I would look into getting that Vetus strainer installed correctly. I believe it needs to be installed at the waterline somewhere. Check the documentation carefully. The Vetus strainer will not introduce the issue in my opinion.

Karlos
29-08-11, 12:44
Timmfive, just a brief thank you for such a great write-up.

Especially for including the diagnostic trail, and the wealth of detail.

In respect of cam size, I'd speculate that, the thicker the cam, the more wear it will impose on impeller vanes (bend further and probably break more). So if in any situation I had a choice, I'd opt for a larger pump and a less thick cam over the reverse.

ianat182
29-08-11, 15:47
The Vetus Raw water strainer need to be fixed at 8" above the waterline.Put Vaseline or grease on the threads to make it easy to undo and check each time,and fit in an accessible position for regular checking.

ianat182

timmfive
31-08-11, 10:51
So if in any situation I had a choice, I'd opt for a larger pump and a less thick cam over the reverse.

Cheers Karlos, glad you found the post helpful. Took me awhile to compile! :)

I appreciate what you are saying, but personally I would rather opt for a pump that works, and is able to prime any air that accumulates in the intake hose, and have to replace the impeller as per normal maintenance. Rather than have a pump that is gentle on the impeller but doesn't work as designed.

Halo
31-08-11, 13:57
I would think twice before putting a raw water filter into a Yamnar 3Ym30 or similar. A lot of people have reported overheating and delays in self priming as an issue. If a filter reduces flow, prevents self priming or blocks up you may have an overheating problem at a very inconvenient time. Better to service or replace the pump when it wears out IMHO
Cheers
Martin

eagleswing
04-09-11, 15:01
congratulations on a brilliant solution to a very challenging problem.. can you imagine how much aggravation you have saved yanmar owners ? i can imagine that even freshwater (antifreeze-cooled) yanmars may experience overheats if the raw water pump has been worn excessively over time by sucking up a lot of sandy water .

fair wind, calm seas

eagleswing port of erie pa usa

timmfive
10-09-11, 20:09
Cheers! Was the least I could do. It took a bit of effort to sign up for a username/account and compile the post and put it together, etc. But if it helps one other person then my work is done here. :-)

jwilson
17-11-11, 18:44
What a great posting!!

If this is the same as the problems on some 3YM30's then you will have answered some more intermittent overheating problems!!

Thanks a lot for the insight

Martin
The 3YM30 overheating problems started with virtually new engines (under 100 hours running in some cases). Despite Yanmar fitting a bigger heat exchanger at 120 hours on mine under warranty it can still be persuaded to overheat occasionally at times with prolonged high throttle. Easing the revs back to 2000 for a minute shuts up the alarm fairly quickly.

Some years ago I queried this with the importers Barrus at a Boat Showm and they professed ignorance of any overheating problem on 3YM30s, despite it having been them that paid the local Yanmar agent to fit the bigger heat exchanger (which is now the standard fit)

Upnorth
04-01-12, 17:37
Sorry to resurect this thread but I am a little confused (situation normal) as to the water pump that is fitted to my 2GM20 engine. It is raw water cooled.

On reading the above, and other threads, as my engine does not have an ‘E’ in front of the engine number, I assume that the water pump is NOT a Johnson pump. If, therefore, it is a ‘Yanmar’ pump, who made it for them? – does anyone know.

Secondly, if my pump should fail, can I replace it with the Johnson pump (F4B-903).

Thirdly a question about fitting a new impellor. Is any gasket sealant needed when fitting the new paper gasket?

jfkal
05-01-12, 02:14
My 3GM30 raw water cooled came ex factory with the wrong pump (fresh water version).
Engine overheated as well. Yanmar changed it for me FOC after some prodding. I carry two spares :-))





Keywords / Title:
Yanmar 3GM30 raw water cooled (RWC) Johnson pump raw water pump failing to reprime, causing engine to overheat.

We had this intermittent problem for almost 1 year.
What follows is my trials and errors, and ultimately a solution to this issue.
I am hoping this will help others out there as there seem to be alot of threads outlining the same/similar issue... but no solution found.


Problem:
- Engine overheating in rough seas, confused seas, and sometimes with steep following seas.
- Due to above circumstances, the engine would often overheat when approaching land, or when the wind died completely but left some sea state behind. Either scenario is the worst time to not have your engine!
- Explained the circumstances that caused the overheating to previous owner. He never had the issue in 13 years of running the engine.
- Also, we didn't have the issue during the first 6 months of having the boat.
- So issue must be new, or I must have introduced it during maintenance in some way.
- Quickest way to resolve issue was to undo supply hose on the intake side of the pump, let air/water drain out into bilge until solid column of water, reattach, start engine, let cool. Continue for another 15-20 minutes or so... hope... :(


Engine / pump specs:
- Yanmar 3GM30 raw water cooled. 13 years old. (Would estimate ~4000 hours?)
- Pump is a Johnson Pump F4B-902, 10-24509-02. Impeller Johnson 810B.


Actions taken:
1) Rebuilt pump completely. Same issue.
2) Threw a few new impellers at it: same issue.
3) Systematically ruled out backplate, paper gasket, intake filter, hoses, air leaks, back pressure, exhaust manifold/gooseneck etc.
4) This year, we replaced black intake hose with clear one to observe water/air flow.
Naturally on heel angles above 20 degrees, air would accumulate quickly and pump wouldn't reprime.
However, even on on 5-10 degree angles but with steep seas, small bubbles from the breaking seas would slowly accumulate. Eventually they would reach a stage where the pump would fail to reprime.

So with the clear hose I was able to observe the issue... why was it happening? Why can't the pump reprime? Why doesn't it just suck through the air bubbles as it goes along?

5) Experimented with different routes of the intake hose: far below waterline as possible, "S" shapes, loops, etc.
Regardless of intake hose position, air would accumulate.

6) Tried replacing the 3/4" (19mm) intake hose to 1/2" (~12mm). Idea was the thinner hose would introduce more suction. No joy.
(Interestingly, both diameters would empty a bucket of water in exactly the same amount of time!)
Even putting finger on end of intake hose... just doesn't seem to be enough suction in my opinion...



Solution:
- Went to Yanmar distributor with old pump in hand and a pair of calibers to measure inner chamber diameter, as well as Cam size.
- Didn't need calipers to see the cam size on new pump was 2 to 3 times thicker than original pump! :)
- Yanmar agent insisted the pump I had was the one for the fresh water (3GM30F) model and that the 3GM30 raw water pump is a smaller one he showed me.
- However, smaller Yanmar branded pump was ~€500. And exact "like for like" replacement of my bigger Johnson pump was "only" ~€220.
- So a bit of a surprise/confusion, but was reluctant to pay twice as much for a smaller pump.
- Was more logical to get the same pump that had worked fine for 13 years.
- The main thing was seeing the Cam size in the new pump. I will attach pictures.
- Note: the cam in both pumps are not replaceable... (else I would have fixed this last year!!!)

New Johnson pump specs compared to old pump:
- Yanmar p/n 128397-42500

Old Pump: Johnson Pump F4B-902, 10-24509-02. Impeller Johnson 810B.
New Pump: Johnson Pump F4B-903, 10-24509-01. Impeller Johnson 810B-1. (no paper gasket)

Old pump Inner chamber diameter: 50.2 mm. Diameter to cam: 48.25 mm.
New pump Inner chamber diameter: 50.0 mm. Diameter to cam: 46.00 mm.

Old pump moved ~180L/h at 1000 rpm.
New pump moved ~420L/h at 1000 rpm.
New pump moved ~630L/h at 2000 rpm.

(Yanmar manual says it should move ~700L/h.. but doesn't state rpm... and i'm not sure if this is in reference to the smaller Yanmar pump that I "should have", or the one that I Do Have...).
New pump had a noticable, considerable more amount of suction when putting finger on end of intake hose.
So much suction, that I was almost afraid my finger would get stuck on end of hose and I would have to kill engine.
Whereas, with the old pump, the suction was feeble and there was easy to plug hose and unplug hose with finger/palm.

Another test, was with intake hose full with a column of water, holding the intake hose vertically:
Old pump the water would be seen to work its way down thru the pump a slow, but considerable pace.
New pump the water would still work its way down... but very very slowly in comparison.

And *ULTIMATELY*... the new pump would prime anything...
ie: take a dry hose, dip it into a bucket of water, and it would suck the water thru the length of hose.
You could introduce air, etc, at anytime, and it would quickly fly thru the hose, thru the pump and thru the system.

:)

No problems since and we've been in some rough seas, steep seas confused seas, etc. (Aegean Meltemi)
All conditions where before we would wince and wait for the untimely <<bbeeeeeeeppp>> of the engine overheat alarm.
It has take awhile for us to gain trust in the engine in such conditions, but now we have regained confidence. :-)
Any bubbles from breaking seas just get sucked thru. The water coming out of the exhaust is noticably more in volume and power.
I have read that the max heel angle to run the Yanmar is ~15 degrees.
We don't motor when sailing on a steep heel angle.
Just motor when we need to get into a port, or if the wind dies.


Root cause:
- Previous owner took the boat up to the UK thru the French Canals. Had no problems.
- We had no problems in UK, English Channel, North France, etc.
- We took the boat back down to the Med thru the French Canals. Had no problems until once were in the Med.
- (In hindsight!) Reason why the pump cam was worn so much, so quickly:
a) 13 years old...
b) the silty, sandy water in the canals increased wear on cam.
(If the pump is rotating at ~2500 rpm, multiplied by 6 impeller vanes hitting the cam = ~15000 laps of the cam a

minute = 250 laps / second. introducing sandy/silty water makes a quick job of sanding down the cam with rubber vanes)

- - -
Conclusions...

Researched this problem for a solution on the internet.
(Google "yanmar 3gm30 johnson pump" for example.)
Found over 30 threads on dozens of sites that highlighted similar/same issue, but no solutions posted! :( The original poster would disappear, or get sick of people telling them to change the impeller. ;)
I will try and go back to all the threads I found over the past year and point them to this post in case it helps anyone out there.
Least I can do. It was a very frustrating issue as it was so intermittent and hard to repeat.
The conditions that caused the issue weren't condusive to troubleshooting... it was more.. get it working, get to port safe, etc.
Sounds simple now in hindsight... but at the time was hard to pinpoint. The clear hose really helped me understand the issue. Very cheap step in the troubleshooting process. Some of the forums did hint and replacing the pump, but quoted the pump at being €500. The reason I didn't do this sooner was that €500 was a very big expense for us, especially as a troubleshooting step, with no guarantee of resolve.

In conclusion... the pump is easy to take off and take to Yanmar and do a comparison with new pump. Shame the cam isn't replacable as on some pumps. Hopefully the measurements above will help someone out there too.

(See attachment of old + new pump side by side... the picture is worth 1000 words).

timmfive
01-02-12, 20:51
The way I understand the history of this is as follows:

1)
A long time ago... When they were intially launched to market, Yanmar 2GM20 / 3GM30 RWC came with a Yanmar Raw Water pump.
But there was an issue with this pump that Yanmar had trouble rectifying.
I might be wrong here, but whether it was a pump design or an impeller design/manufacture fault, the rubber and the collar inside the impeller kept parting ways...
So it was obviously a big issue and frustrating for the users... especially considering that, on these engines, one has to remove the pump to take off the backing plate to replace/inspect the impeller.
(This issue probably didn't help improve the general overall reputation of "the impeller"... as everyone is always blaming the impeller first thing when it comes to overheating issues, etc. My (limited) experience is, within reason/normal service, the poor impellers can take alot more abuse than people give them credit for! But i digress...)

2)
So... From what I understand, Yanmar outsourced the RawWater pump manufacturing (for 2gm20 3gm30) to Johnson. And I think most people seem to have the Johnson pump (whether they know it or not!). For the few that have the original Yanmar raw water pump, they must be using impellers that have a corrected manufacture or design that eventually fixed problem 1) above.

3)
Now... it seems that the Johnson pump that were used above are currently listed as a "Fresh Water Pump" in the Yanmar parts catalog!
And Yanmar now have a listed Yanmar "raw water pump" for sale also (presumably with fixed design/impeller construction.)
But as per my original post: I've seen both side by side. (Wish i took pictures!) The Yanmar pump had a smaller impeller and inner-chamber dimensions, so presumably pumped less water... and also was twice as expensive.
The Johnson pump was exactly the same as my knackered one (as per the picture in my original post), which had been on the engine, from factory, 13 years ago.
So replace like with like was my gut instinct. (and avoid twice the cost!)

Other ramblings:
The engine thermostat will take care of the water temp, the rest will get pumped overboard.
The only implication i can think of by pumping excessive water would be the exhaust cooling. Where the Raw Water cools the exhaust manifold, and then mixes with the exhaust in the U-shaped fitting...
So if there is some sort of finely tuned engineering they've done to make the manifold + U mixer elbow a specific temperature, then maybe would warrant using their (expensive) yanmar pump with smaller than normal impellers (possibly hard to find in remote areas).
For all I know, pumping more water thru the exhaust, and keeping it cool, will help the coke-ing up problems in the manifold / mixer that most people experience... or maybe it is the source of the problem!
What do I know? But I'm not going to hold my breath that we'll ever fully find out. Most people are on the new 3YM-series engines now anyway...

Perhaps my only warning would be this:
If installing a new Johnson to replace an older Yanmar (or knackered Johnson), either way: be aware that the new Johnson does pump alot of water... so to be sure to close your intake sea-cock before turning over engine with decompression levers off, or trying to manually start for example, etc.
I reckon the new pump will have no problem filling up your Vetus anti-siphon box aft of the exhaust in no time. And noone wants to experience a hydro-static lock!

Hope this helps clear things up, rather than muddy them up.

Hope everyone is enjoying their winter... days are getting longer... can't wait to get back!

parbuckle
02-02-12, 13:00
Considering the high cost of replacement pumps I would look at the possibility of repair to the pump chamber,the old cam could be machined off on a lathe and either have a new cam made up from a pattern or purchase a similar retrofit part from a jabso or volvo pump (these are supplied as seperate parts) and if you can match the impeller diameter and vane width it may be possible to fit the cam from that pump ,these are through bolted from the outside and the construction is far superior (unless your selling pumps),with a repair you may get change out of a 100 quid.

timmfive
02-02-12, 19:54
The Johnson pump I bought from Yanmar was €220 (£180).
(see orignal post for part numbers)

While I agree with your idea about machining out the cam, and installing one of the replacable cams seen in other water pumps... i'm not sure if it is cost effective.

- getting the old pump machined out with a traditional lathe might be tricky due to off-weight, assymetrical pump design. Would require pump be completely dismantled. Migth require creation of a custom mandrel to hold it in the chuck, unless you can find a CNC, etc...
- then measuring, sourcing, fitting new cam, rebuilding pump, etc.

Not trying to be a troll! As i think its a good idea! :-)
but my opinion was that all the spares: pully, seals, impeller, faceplate, pump housing i got for €220 was pretty cost effective.
and i kept my knackered pump in case new pump one day gives extreme fault, can pop in new pump in 10-15 minutes at sea. Versus trying to rebuild various pump bits at sea... would take me an hour or two.

but maybe if you were having to motor in a place somewhere in the world with extreme silt... like a inlet, river, lake, or as it was in my example French Canals... might definately be cost effective if you found you were wearing this cam down every year or two!

- - -

forgot to say to @Upnorth
regarding sealing the backing plate, paper gasket, etc.
again, i think this depends on what pump you have as per my previous post.
but both the old and the new Johnson pump I have use an O-ring. Thats it.
The old pump has flat head screws to secure plate. the slots were getting worn on the heads. The new pump has SS bolts instead, with philips as backup i believe (i'm not on the boat at present).

i've heard all sorts about paper gaskets and hylomar and gasket materials being used during my initial troubleshooting and research. i think it depends on your pump, obviously. maybe orignal yanmar's needed paper gasket.
i ruled out air / water leak by attaching hoses to both ends, plugging one, and blowing in. water leak by close inspection/observation when engine running. my guess would be if your pump was designed with just backing plate meeting pump... no groove for rubber o-ring on pump... then yeah a gasket of some sort, or hylomar type compound would be needed.

parbuckle
02-02-12, 20:38
It is worth discussing all options but £180 for a new pump is probably the way to go,good to see you solved your problem and passed on the information,I have just picked up a used jabsco sea pump for my Perama M20, will stick it in my bottom locker for a spare or maybe fit it now to check it out.