Lack of cooling water, but why??

[pgtips]

Was out at the weekend and on starting the engine to come back in to the marina (Yanmar 1GM10) there was a lack of cooling water, so engine water alarm went off.

Luckily managed to sail into the marina entrance and then got a tow back to my berth from the marina workboat.

First thing I checked was that water was getting in to the system, so checked filter in seacock, which was clear and on opening seacock, plenty of water coming in, so nothing blocking the intake.

Next job was to check the impellor, which seemed okay, but changed it anyway and then started engine. Still no coolong water from exhaust!

Thought that perhaps water pump packed up, but only had a new one about 18 months ago, so then thought that I hadn't checked that the impellor was actually turning and decided to take water pump cover off and turn engine by hand.

At the same time also put some grease on the impellor face, as hadn't done this the first time.

Turned engine over using starting handle and impellor turned, so put cover back on, started engine and now water out of exhaust.

Ran engine in gear for 10 minutes or so and no overheating, plus cooling water continued to flow so would appear to be okay, but I'm now bit concerned as to what caused the problem in the first place as don't really want it happening again.

The engine had been running fine when I motored out of the marina in the morning, so it seemed a bit weird that fine when turned off, but problem straightaway on starting up.

With the cooling system on a 1GM being fairly basic, is there anything that could cause an obstruction, but then clear itself?

Would the lack of greas on the impellor face be enough to stop it turning? I'm assuming not as I can't believe that the water pump cover would be that tight to stop the impellor turning, but this seemed to be the only thing I did differently that then seemed to "cure" the problem!!?

 

[LittleShip]

Was out at the weekend and on starting the engine to come back in to the marina (Yanmar 1GM10) there was a lack of cooling water, so engine water alarm went off.

Luckily managed to sail into the marina entrance and then got a tow back to my berth from the marina workboat.

First thing I checked was that water was getting in to the system, so checked filter in seacock, which was clear and on opening seacock, plenty of water coming in, so nothing blocking the intake.

Next job was to check the impellor, which seemed okay, but changed it anyway and then started engine. Still no coolong water from exhaust!

Thought that perhaps water pump packed up, but only had a new one about 18 months ago, so then thought that I hadn't checked that the impellor was actually turning and decided to take water pump cover off and turn engine by hand.

At the same time also put some grease on the impellor face, as hadn't done this the first time.

Turned engine over using starting handle and impellor turned, so put cover back on, started engine and now water out of exhaust.

Ran engine in gear for 10 minutes or so and no overheating, plus cooling water continued to flow so would appear to be okay, but I'm now bit concerned as to what caused the problem in the first place as don't really want it happening again.

The engine had been running fine when I motored out of the marina in the morning, so it seemed a bit weird that fine when turned off, but problem straightaway on starting up.

With the cooling system on a 1GM being fairly basic, is there anything that could cause an obstruction, but then clear itself?

Would the lack of greas on the impellor face be enough to stop it turning? I'm assuming not as I can't believe that the water pump cover would be that tight to stop the impellor turning, but this seemed to be the only thing I did differently that then seemed to "cure" the problem!!?

I had a problem going into Pwhelli marina years ago. engine alarm went off so I stopped the engine, a plastic bag then floated away from the rear of the boat.

I would think that you have suffered the same problem ?

I now always pick up plastic bags that I see when around the marinas.

Tom

 

[mattonthesea]

I once chartered a yacht with a Volvo Penta (so might be different) that had the same problem. Investigation proved it to be an impeller that had worn on the side against the cover plate. Or the cover plate had worn. Anyway, it menat that if the water trap seal was broken by opening to inspect then the impeller would lose its priming and cease to work. A tine bit of grease made all the difference.

Not sure if this helps

Matt

 

[pgtips]

Matt,

This does sort of make sense as although the impeller seemed okay, it was slightly worn on the edge against the cover plate, so perhap that was enough to lose the seal. I just thought I would have still got some water being pumped even if the seal wasn't perfect, but not being a qualified engine mechanic, what do I know??!

Anyway, Speedseal cover on order to make any future changes/inspection easier as couldn't really do this when out sailing due to rather choppy seas and fiddly screws on cover plate!!

Thanks for the reply and just hope it was a one off.

 

[chewi]

Could also be a small split in the feed pipe from the oggin to the pump. A small leak can enough air in to prevent the pump from priming.

 

[SAWDOC]

Check that there are no kinks in your water intake hoses which might prevent flow when you have everything back together.

 

[tt65]

Speedseal on my Bukh DV24 and some questions.

Interesting. I did a bit of servicing to my Bukh 24 during last week, oil, filters anodes etc. (Engine has the commonly used Johnson pump) I replaced the water pump impeller and there was no water thereafter. I have a Speedseal so I replaced O-ring which felt flat. Still no water. I examined the Speedseal plate closely and decided it had a significant amount of wear. Replaced again the impeller and put on the pump's original cover plate with the paper gasket and then got a good water flow. That is the way I have left things.

I never thought of grease. Would this normally be a part of replacing the impeller procedure does anyone know?

I don't recall ever having applied grease when replacing the impeller. Should I replace the Speedseal, this time with grease?

Can a Speedseal face plate wear to the extent that it will not function does anyone know?

In the 20 years using this Speedseal I have never actually had to remove it in a hurry so not sure if there is a real benefit in the things. Any experiences out there of the Speedseal being a benefit rather than a gimmick?

I have got 7 or 8 impellers now, all of which fall into the category of "used but good". I have never actually thrown one away as they seem to show no actual signs of wear, I simply recycle them and never had a problem before. but does anyone know how to identify a poor impeller? Measurements perhaps?

 

[TonyS]

A possible solution

I used to have this problem on a 2030. Sailing would suck the water out of the cooling system as air was admitted by the anti syphon valve. The pump vanes did not provide a seal in the pump. Grease will be a temporary solution. It could of course, in your case, be a plastic bag. With a sail drive, you can motor in reverse and any obstruction will often lift off. The effects of no water are tears in the vanes and failure of the water seal in the pump. The seal should last thousands of hours but often fails as a result of no water and no lubrication in under a thousand. My solution, as I probably had a badly machined pump, was to fit a spring assisted SS non return valve positioned above the water line just before the anti syphon valve. These NR valves cost about £5 but you also need adaptors and clips adding another £5. Larger engines with bigger pumps do seal and do not need this mod. I found this out by fitting a flow switch in the cooling system connected to a siren. Now the siren stops instantly. If you look at my posts you will find a picture of the set up.

 

[pgtips]

Thanks for the replies on this and hopefully a careful check of everything now it's all back together will prevent future problems.

Tim - the reason I put some grease on the impeller is that the engine manual I have says this is the thing to do, although I can't remember doing this when chasing impellers previously and they've worked ok before.

Perhaps when things wear slightly, the grease is enough to create the seal??

The main reason I've gone for the Speedseal is that the the top bolt on the water pump cover is quite fiddly to get at, so am hoping the Speedseal will make life a bit easier!?

 

[richardabeattie]

I've always fancied a speed seal for my Yanmar GM20 but thanks to intelligent design the waterpump faces aft. Seems to me that even with a speed seal I 'd still have to get the pump off and turn it round to get at the impeller. Or is there a way?

 

[cid]

impellers

Hi Richard I recently found a web site that describes this for your case.To put it simply you close the inlet seacock.Loosen clips on both hoseson impeller.Remove belt from pulley.Unbolt unit from main engine block and then rotate it till the pulley is at the back and plate is at front.Then work away.The web site was www.boat wizard.blogspot.com
Regards CID

 

[Scotty_Tradewind]

Twice I've had reason to be grateful for having a SpeedSeal.
With an aft facing impeller cover and with screws that were in such a position that even a stubby driver could not fit, it made good sense to change.

My latest experience was when a minor split on the intake pipe at the base of the impeller pump caused air to get in but very little water to get out, causing overheating.
The impeller had lost a few bits and had to be replaced.

 

[Cliveshep]

Grease is a very short term fix indeed, perhaps helpful until the new impeller beds in but will in a few revs find it's way further up the system. Water lubricates pump impellers.

Make sure no air leaks anywhere on the suction side, don't know about Speedfit plates but on the normal Jabsco type pump you can reverse a worn cover plate.

Any grooving or "dishing of the cover plate is wear you do not want - chuck it away and replace it.

Why can you not reverse the pump to face forwards? Impeller blade tips "trail" the centre when rotating and pass over the cam which squeezes them together. When they pass the cam and spring back out it creates a suction between them which is what pulls water up the inlet pipe, being squeezed against the cam as the impeller turns forces that water trapped between the blades out the outlet pipe. Theoretically at least pumps can be reversed and the connections reversed, why not look into that to make accessing the cover plate easier?

Sorry, don't mean to "teach Grannie to suck eggs" here!

 

[30boat]

Grease will break up the impeller very quickly.Use Vaseline instead.I always refit my impeller this way.The one time I used grease it didn't last long.

 

[richardabeattie]

Hi Richard I recently found a web site that describes this for your case.To put it simply you close the inlet seacock.Loosen clips on both hoseson impeller.Remove belt from pulley.Unbolt unit from main engine block and then rotate it till the pulley is at the back and plate is at front.Then work away.The web site was www.boat wizard.blogspot.com
Regards CID

Welll yes that is of course what I do - but my question was what's the point of a speed seal if you have to take the pump off anyway? Getting the pumpp off and back on takes the time. Once it's off taking the plate off and putting it back with the screws as supplied is only a small part of the job so I feel the Speed seal is not worth it for 2GM20

 

[KREW2]

I had a similar problem a few years ago, all seemed well and impeller turned ok with the hand crank. I decided to change it anyway only to discover that metal hub of the impeller was loose, so under load the blades did not spin.

 

[pgtips]

I had a similar problem a few years ago, all seemed well and impeller turned ok with the hand crank. I decided to change it anyway only to discover that metal hub of the impeller was loose, so under load the blades did not spin.

Now that would make sense! Think I still have the old impeller so will check to see if the centre metal section is loose. Thanks.

 

[Vara]

Grease will break up the impeller very quickly.Use Vaseline instead.I always refit my impeller this way.The one time I used grease it didn't last long.

Vaseline (petroleum jelly) may also degrade some impellors, best to use glycerine/washing up liquid / ky jelly. My understanding is that any lubricant is just to ease the turning of the impellor until water reaches it. effectively self lubricating after that.

 

[prv]

I've always fancied a speed seal for my Yanmar GM20 but thanks to intelligent design the waterpump faces aft. Seems to me that even with a speed seal I 'd still have to get the pump off and turn it round to get at the impeller. Or is there a way?

I don't think there is. I've been through exactly the same thought process as you, and have decided simply to carry a 7mm nut driver (slightly quicker and easier than a screwdriver) rather than fit a speedseal.

Hi Richard I recently found a web site that describes this for your case.To put it simply you close the inlet seacock.Loosen clips on both hoseson impeller.Remove belt from pulley.Unbolt unit from main engine block and then rotate it till the pulley is at the back and plate is at front.Then work away.

So what you're saying is that to work on the 2GM20 water pump you have to unbolt it and turn it round? Thanks, but to anyone who's looked at the thing that's blindingly obvious. In my case, though, there is no need to loosen any hose clips (closing the seacock is recommended though if you're going to take the cover off!).

Why can you not reverse the pump to face forwards?

This might be possible in some installations, but it puts the pump body quite some way further forwards. In my case there is not nearly enough room. I believe someone does sell a metal bracket to help with this flipping, although it does rather put the pump "out on a limb" which looks a bit less robust.

Grease will break up the impeller very quickly.Use Vaseline instead.

One of the spare impellers I inherited came with a little sachet of grease, which I assume is suitable for the purpose. I wouldn't use vaseline; I've seen it eat bike inner tube rubber in a matter of days.

I feel the Speed seal is not worth it for 2GM20

I agree.

Pete

 

[chrisedwards]

I had a similar problem on my yanmar IGM a few years ago. Cooling water just would not come out - checked inlet,seacock,pipes and pump - fine. Took exhaust off manifold and water coming out ok - put exhaust back on - no water. Blew through exhaust - clear. Exhaust back off - ah water enters exhaust via "slit" along side of manifold. When I slid exhaust on the perished inner part formed a blockage which could be intermmittant. New exhaust pipe - fixed.