Solved! Overheating Yanmar 3GM30 due to Johnson raw water pump not priming.

[eagleswing]

brilliant!

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]

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]

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]

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]

Yanmar Oh My

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]

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]

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]

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]

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.

 

[ajaxpc]

Re: Solved! Overheating Yanmar 3GM30 due to Johnson raw water pump not priming

Hi timmfive - many thanks for your post, which saved me a lot of pain. I didn't have the priming problem, but did have a worn (and replaceable) cam. See:

http://raasay-of-melfort.blogspot.co.uk/2015/06/engine-cooling-pump-cam-problem.html

I would never have figured this out on my own ...

 

[masterman ready]

Hi
I realize this is an old thread but you never know who it may come in handy for.
I have been having problems with the water pump on my recently bought Jaguar 25, the engine is a 2gm20 and the pump on it is the same as yours a Johnson F4B-902.
I have been having a lot of difficulty getting it to prime (its out of the water at the moment) I have a T off from the intake hose to put into a bucket, when it does eventually prime with much fiddling about with funnels etc the flow is ok but not great, then when I come back the next day back to square one.
After much internet searching, looking at various kits to rebuild which may or may not work I found your post, thank you for the detailed information as no one else dealer or other could tell me what the inner housing thicknesses should be. on measuring mine they are 50 mm main body and 51 mm to the cam ! so I don't think any amount of rebuild would have helped as the cam is part of the actual housing and not replaceable.
Lastly I wondered where you got yours, I know it was a while back, the cheapest I can find is from pump marine power at £320 including VAT.
once again thank you for the time and effort that you put into your original post
Regards
Mark