Yanmar 3YM30 cooling problem

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RHWeisberg

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My engine functions OK when first started. After shutting and sailing for the day, it will not draw cooling water upon restarting. All hoses from intake to heat exchanger appear to be clear, the impeller is turning, pump was recently rebuilt, heat exchanger was cleaned and lifting elbow was replaced. Any suggestions on what may be the cause?
 
Does the pump start to work if you pour water into the strainer mesh and then replace the cap? If so, the pump is not priming properly and it's not uncommon.

There might be an air leak upstream of the pump so make sure that there is a good rubber seal on the strainer and plenty of silicon grease/vaseline on the seal and lid and the hoses are all nipped up right back to the seacock so no air can get in. When the engine is stopped and left for a few hours, you should still see that the strainer is full of water, assuming that you have a transparent screw top.

If there are no air leaks, remove the pump cover plate and smear plenty of silicone grease/vaseline all over the impeller, the inside of the pump and the inside of the cover plate. If the pump primes fine after that, then you simply need to keep it well lubricated or the new impeller is the wrong one or the cover plate/pump cam are worn.

Richard
 
It's unlikely to be the impeller but the cover plate on the 3YM30 pump is very prone to wear and corrosion. It's a good idea to clean it up and polish it annually. I find I need a lot of revs to get it primed at the start of the season. I had thought the water was draining back out when the engine stopped but the water was so clear I couldn't see it. I've spent this season with a cork floating in the strainer and to my surprise it's stayed full for the whole season. If it's not the cover plate then there is likely to be an air leak. Check the hose clips are tight. The impeller is very robust. I know a lot of people change them anually but Yanmar give it a 1000 hour life. I usually change mine every 5 years or so.
 
I cleaned the sea water strainer (it was clean) and heavily greased the o-ring, and I removed the pump face plate, heavily greased the o-ring and greased the inner portion of the face plate.
Since all of the water between the heat exchanger and the pump drained when I removed the face plate, I realized that it would take time to self prime. I let it run for awhile on my first try and increased rpms a few times without success. I then waited while doing other chores and tried again. It then primed and started pumping water. I let it run for about a half hour while servicing my A/C filter, shut it down waited and then restarted. It worked again. But did the extra grease on the o-rings stop any air form leaking in, thereby correcting the issue, or will it happen gain the next time I use the boat? I am less than confident.

My thoughts are:
1) I fixed it (I hope)
2) The rebuilt water pump seals are letting air in.
3) The drain hole on the hose between the pump and heat exchanger is leaking air (I doubt that because if it was leaking air wouldn't it also leak water).
4) The anti-siphon device (between the heat exchanger and the lifting elbow) is malfunctioning.
5) The heat exchanger has a blockage (but it was recently rebuilt).
6) The small elbow going into the lifting elbow has a blockage (but it was changed when the lifting elbow was changed).
7) Is is simply a matter of the cover plate being a little worn.

Thanks again for the previous suggestions.
 
RHWeisberg said:
I cleaned the sea water strainer (it was clean) and heavily greased the o-ring, and I removed the pump face plate, heavily greased the o-ring and greased the inner portion of the face plate.
Since all of the water between the heat exchanger and the pump drained when I removed the face plate, I realized that it would take time to self prime. I let it run for awhile on my first try and increased rpms a few times without success. I then waited while doing other chores and tried again. It then primed and started pumping water. I let it run for about a half hour while servicing my A/C filter, shut it down waited and then restarted. It worked again. But did the extra grease on the o-rings stop any air form leaking in, thereby correcting the issue, or will it happen gain the next time I use the boat? I am less than confident.

My thoughts are:
1) I fixed it (I hope)
2) The rebuilt water pump seals are letting air in.
3) The drain hole on the hose between the pump and heat exchanger is leaking air (I doubt that because if it was leaking air wouldn't it also leak water).
4) The anti-siphon device (between the heat exchanger and the lifting elbow) is malfunctioning.
5) The heat exchanger has a blockage (but it was recently rebuilt).
6) The small elbow going into the lifting elbow has a blockage (but it was changed when the lifting elbow was changed).
7) Is is simply a matter of the cover plate being a little worn.

Thanks again for the previous suggestions.
Click to expand...
It sounds to be as if you have, in effect sorted the problem. If it primes next time, it was probably the strainer but, if it's got a clear top, you will see if it's still full of water. If it is full of water, but the pump still stops woringk properly, I would bet that if you grease the impeller and pump it will start working again.

My pumps are also very iffy if I remove the strainer top and break the vacuum. If I then grease the pump everything is fine until I release the strainer top again.

Richard
 
The long expected failure at sea finally happened. Fortunately I noticed the change in engine note. The pump is now on my workbench dismantled. Its done 1300 hours. There was no water leak. It looks like the shaft seal has failed and I suspect this was letting air into the system as it was difficult to keep the strainer filled. The pump flow was too low to displace all the air from the strainer. The shaft is in perfect condition but looks like the inner bearing is close to failure. The inner face of the body has been scored by corrosion debris from the seal spring. It appears that the original seal spring is not stainless. I'm very surprised that it lasted 12 years. It looks as if its worthwhile changing the seal well before it starts leaking. It might be worth adding to the 500 hour service. There have been posts about the necessity to change the shaft. I had a spare shaft aboard but I think this is completely unnecessary if the seal is changed regularly. Hope this helps anyone else with this pump.
 
been through that...
when checking the seal, you'll indeed find that the spring is mild steel. My mechanic threw it away and replaced it with a suitable sized oring - well smaller so that it introduces some pressure to the lip to seal on the shaft. Unconventional I know, but seems to work
100hs later all is fine (touch wood!)
TBH, having a shaft onboard as a spare is slightly pointless as you cannot easily replace it, need new bearings and a press to fit them plus the new seal. Unless you have them all fitted on the shaft hoping you'll be able to remove the old one and refit without issues.
 
Yes I was surprised the spring wasn't stainless. It's possible it fails very quickly and reduces the efficiency of the pump. Not sure if the state of the lip seal affects the pumps ability to pump it's specification head.
 
You don't need a press to fit the bearings. It's a simple job with an on board vice and socket spacers.
 
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