1GM10 Engine Running Very Hot

[langstonelayabout]

My 1GM10 engine is running very hot. It does run properly: no black soot or steam.

I’ve checked the entire cooling water system (from the inlet seacock, the tubing through and including the water pump, into the engine and into the thermostat) and finally to the exhaust elbow which, (like the cylinder head) is nearly new.

There are no restrictions in any of the tubing but there also doesn’t seem to be that much water coming out of the exhaust…

Because of the excessive heat it prompts a couple of questions…

1 The pump impeller is new. If I’ve installed it with the lobes pointing the wrong way will that reduce the quantity of water that will be pumped through the engine?

2 The thermostat. I’ve not had the chance to check it works correctly. The rest of the boat is 25 years old. Should I change it out of course as its failure could cause this type of problem?

Could there be any other concerns causing this problem? I restarted the engine a couple of minutes after stopping it yesterday and the water temperature alarm sounded for nearly a minute before silencing itself (No, I hadn’t closed the seacock).

Your thoughts please?

 

[Jabs]

Take the cover off the sea water pump and turn the engine over to check it's going the right way.
How hot is hot? Can you put your hand on the exhaust elbow?
My gm10 ran so cold it was a worry.

Have you checked the anti syphon box for obstructions?

How quickly does it get hot?

Is the oil level ok?

How is the fuel consumption?

Do you run it hard?

Is it very over propped?

I would suspect reduced cooling water flow.
If it's really hot after a run and you restart it, it's a miracle that the block isn't cracked through the sudden influx of cold water.

Remove the thermostat completely and see how it runs.

Keep us informed.

Good luck

Tony

 

[sparerooms]

I was just about to post the same question about my Volvo Penta MD11!

I checked the thermostat and it is all corroded.
Can I remove the thermostat completely? Will the engine run OK without it?

Sorry to hijack you post :-/

 

[VicS]

If there is not much water coming out of the exhaust and there are no obstruction to flow anywhere the pump is suspect.

You have fitted a new impeller ( it does not matter if you fit it with the vanes facing the wrong way ... it will soon sort itself out)

Have you checked that the impeller is being properly driven. Dont know if it will apply to the Yanmar but they some times become unbonded from the hub.

Check the pump for wear.


Test the thermostat by all means. Check that it is the right type and that it begins to open at the marked temperature (52C ??) and is fully open 14C higher.

DO NOT run without the thermostat . When it opens it also closes the bypass thus ensuring water flows through the engine. If you run without it nothing will be closing the bypass and the engine will overheat.

I do not believe this applies to a raw water cooled MD11... but may apply to an indirectly cooled version.

 

[Tranona]

VicS has covered most points. However, also check you are not getting air in the intake from such things as loose clamps on hoses or cracks in water filter. If you are not getting flow out of the exhaust then it is either air coming in or a blockage in the engine. The most common points for blockages on the 1GM are the vertical bypass hose and the fitting that takes the water into the bottom of the cylinder. A stuck thermostat is also a possibility.

 

[Appledore]

Hi,

You don't say if this is a recent occurrence, or has been evident for a while. However, if your engine is running hot, then the alarm should sound. The day before leaving for France last summer, I had my 1 GM10 engine running whilst I checked things on deck. The alarm suddenly sounded, and I really didn't know why, as the water discharge (checked on starting up) seemed to be as normal. Not wanting to get caught out, I bought a new thermostat and engine water heat sensor (together with a new anode, which is easy to fit as you have to remove alternator to replace heat sensor!). Having spoken to the local marine engineer at Wier Quay, he recommended flushing the engine with a de-scaler (can't remember what it was called, but other forums have recommendations, such as drain unblockers!! I had to remove the new thermostat to allow circulation, and s l o w l y pour the liquid into the engine, using a small funnel and a length of tubing. Oh yes, I did also remove the impeller first as the liquid could damage the rubber I was told. Left in overnight, and flushed out in the morning, the alarm has remained quiet since (Shhhhh!). The water temperature sensor was completely furred up by the way, and there was nothing left of the old anode!

I can't say that this is or could be the cure for your overheating, but it will certainly clean out all the gunge in the engine. I think I used just less than a litre of the cleaner.

Geoff

 

[prv]

I don't know the relative likelihood of the possible problems, but the thermostat is fairly easy to check so you might as well. Simply put it in a pan of water on the stove, with a thermometer in, and heat it up. Keep an eye on it to see when (if) it opens, and check the temperature.

I did this a couple of years ago with the thermostat in my VW Polo when it overheated driving home from work (nursed it home by stopping repeatedly for it to cool down). In the pan, it never did open. I bought a new one for a few quid on eBay, and before fitting it I did the same pan test to check my diagnosis. The opening was clear and easy to see, very distinct from the failed one. Installed it in the car and all was well.

Pete

 

[langstonelayabout]

Many thanks one and all. I'll be rinsing the engine out, fitting a new thermostat and new impeller this weekend.

Fingers crossed...

 

[Appledore]

Many thanks one and all. I'll be rinsing the engine out, fitting a new thermostat and new impeller this weekend.

Fingers crossed...

Hi,

As I mentioned, pour the de-scaling liquid in very slowly as it will tend to fizz up like a shaken-up can of cola! Obviously, you need to pour it in from above the cylinder head height. I used a same size hose onto the thermostat inlet, and a very small funnel.

Good luck, and do let us know if there was any improvement.

Geoff

 

[Appledore]

Bumping this thread up for, hopefully, an update from OP, Langstone

 

[langstonelayabout]

And you've ended up with a response from me instead...

I've changed the thermostat and it's made s*d all difference, however the more I read on other forums, the more I think it's the water pump. Which horrifies me because a new one is £250, a rebuild kit £150...

There's not much water coming out the exhaust which makes me think that the pump really isn't pumping. I rebuilt the pump with a new pattern impeller and cardboard gasket but have considered that the front plate of the pump is slightly dished (wear) and that the thicker card gasket is letting the water past the side of the impeller.

Marine Power in Gosport may soon be £250 better off...

Over to the OP with their Volvo engine solution...

 

[Appledore]

And you've ended up with a response from me instead...

.

Sorry, but I thought you were the original poster, 'Langstonelayabout'?

And very sorry to hear you still have a problem. Could you not get someone to make you a replacement brass plate before spending out that kind of money? There must be someone in the area who does light engineering who could make one up in a few minutes. If I remember correctly, it's only a flat plate. You could then fit that and see if it makes a difference to the water supply. As you have already observed, you do really need a very thin gasket, or even try it without, using a smear of some sort of jointing compound. Could you try reversing the existing plate? Clutching at straws here, but thinking of you spending money unnecessarily.

 

[Tranona]

And you've ended up with a response from me instead...

I've changed the thermostat and it's made s*d all difference, however the more I read on other forums, the more I think it's the water pump. Which horrifies me because a new one is £250, a rebuild kit £150...

There's not much water coming out the exhaust which makes me think that the pump really isn't pumping. I rebuilt the pump with a new pattern impeller and cardboard gasket but have considered that the front plate of the pump is slightly dished (wear) and that the thicker card gasket is letting the water past the side of the impeller.

Marine Power in Gosport may soon be £250 better off...

Over to the OP with their Volvo engine solution...

The pump is very simple and does not normally wear except the seals on the drive shaft, which do not affect pumping. Your cardboard gasket is not helping. The original is thin paper (although priced as if it were gold) and that affects the end clearance on the impeller. Before you splash out on a new pump, buy a Yanmar impeller and treat the pump to a Speedseal front cover which seals with an O ring. Not only is it a better seal but does away with those fiddly little screws.

 

[Mel]

Have you checked the suction side of the pump. A blockage can happen if you have been sitting in mud for instance.
Take off the strainer lid to see how much comes through - you can turn off the sea cock if the lid does not go back easily.

 

[onesea]

Davied crawford in Lymington does impellers and gaskets at not unreasonable cost...

I just turned the front plate around to give me another few years out of one plate... Some where on here I saw a link to front plates for about 15 quid....

 

[aquaplane]

I measured the water flow by catching it for a minute in a bucket under the exhaust. Before I did anything, there was a little over a liter a minute coming out with the exhaust.

after a couple of acid washes through the engine it went up to about 2 liters a minute.

First job, measure how much water is getting through the engine then you know if you have made any difference when you have done somat.

I agree with the "don't run without thermostat" statement, it's not a cure and it lulls you into a false sense of security.

More words here:
http://www.westerly-owners.co.uk/woaforum/viewtopic.php?f=2&t=2851

 

[sailorbaz]

The pump is very simple and does not normally wear except the seals on the drive shaft, which do not affect pumping. Your cardboard gasket is not helping. The original is thin paper (although priced as if it were gold) and that affects the end clearance on the impeller. Before you splash out on a new pump, buy a Yanmar impeller and treat the pump to a Speedseal front cover which seals with an O ring. Not only is it a better seal but does away with those fiddly little screws.

I replaced the seals in mine during a recent refit - there is a thread with a link to a series of photos of how to do it, which I can't find at the moment. I also bought the Speedseal kit and with a new impeller it definitely improved the flow.
Sailorbaz

 

[Spyro]

I measured the water flow by catching it for a minute in a bucket under the exhaust. Before I did anything, there was a little over a liter a minute coming out with the exhaust.

after a couple of acid washes through the engine it went up to about 2 liters a minute.

First job, measure how much water is getting through the engine then you know if you have made any difference when you have done somat.

I agree with the "don't run without thermostat" statement, it's not a cure and it lulls you into a false sense of security.

More words here:
http://www.westerly-owners.co.uk/woaforum/viewtopic.php?f=2&t=2851

You can run without a thermostat at a push but you have to physically block the short bypass hose that runs from the T piece to the thermostat housing.

 

[PeteCooper]

One problem I've heard of on the 1GM10 is that the impeller appears to be fine but in actual fact the central metal part can spin in the rubber(or whatever it is) so it looks OK but in use only the centre turns and not the bit with the vanes.

 

[davidbfox]

I refitted the pump on my Yanmar and did not properly tighten the hose at the pump. The engine ran hot and smoked. The only evidence of leakage when the engine was stopped was a drip every five seconds or so, but the impact on pumping was dramatic. Remaking the hose joints at the pump solved the problem.