IGM10 heating

[Impaler]

Started to get a high temp alarm following a dry out for anode change. Checked the flow path from skin fitting to pump and thermostat and they are clear. Thermostat seems to work OK though it was a bit gunged up. Impeller rotates, I took off the Speedseal cover and manually turned her over and it is turning. However no water is flowing through the system.

Is it possible for the impeller to turn but not pump? I have ordered a new one just in case and will give it a whirl when it comes.

 

[philip_stevens]

Is the lid of the filter on properly and sealed. If not, it can draw in air and not water.

 

[Impaler]

Yes, that's OK, I have checked that everything is tight.

 

[pete]

I have had the same thing with my 1Gm10 some times (it is moored on a drying mooring) I think it airlocks and the puny pump cannot get rid of it. Usually stopping the engine and starting it again helps. I have fitted a water flow alarm and a exhaust temperature alarm to the system now but I was finding some times the old impeller worked better than the new replacement one. my engine did not like the Globe (run dry ones) so I inspect the old impeller each season and leave it in if it is ok. I carry a couple of spares for emergency. But after a fast sail with the boat healed over it is as if all the water has been sucked out of the engine.
pete

 

[Tranona]

First thing to check is the short bypass hose. That is the one that goes from the T fitting above the pump to the thermostat housing. This is where the water goes before the thermostat opens. That blocks easily with crud, as does the T fitting that goes into the block. These are the first places to clear.

If the impeller is going round then it is working. When you take the outlet pipe off the pump and turn it over by hand with the decompressor up, you should get water out. If not then there is probably air getting into the system before the pump.

Hope this helps

 

[Impaler]

Thanks, I'll have another look on Wednesday. Banff harbour was freezing over today and my enthusiasm was diminishing. -15 up here last night. Oh and I did check for ice in the pipes!

 

[jerryat]

>> Impeller rotates, I took off the Speedseal cover and manually turned her over and it is turning. <<

Have you also checked that all the impeller blades are there and are complete? A tiny bit, jamming in the pump outlet will happily block the flow!

 

[Impaler]

It's all complete, nothing missing. I am convince it's airlocked or something but can't trace it.

 

[Slinky Spring]

I once found that there was a blockage in the block. I removed the thermostat and pushed a screw driver gently through the tube behind it. A gentle shove and it broke through a crust of salt and water started running out of the hole. Might be worth a check.

 

[steve28]

another vote for the bypass hose, squeeze it and see if its crunchy. Also you can try blowing through the hose from the pump. see if you can blow easily.

steve

 

[vyv_cox]

It sounds to me like the pump is not priming. Happens quite often when you change impellers, especially if the front cover is a little worn. If you have a strainer between the seacock and the pump, fill that with water with the seacock closed, tighten the strainer lid down, open the seacock then start the engine.

As someone else said, it sometimes happens when sailing in boisterous conditions that the suction pipe will drain. I tried a check valve, closing the seacock when sailing, but neither worked. In the end I refaced the pump cover and the problem went away.

 

[awol]

Been there - I found that a bit of grease on the cover plate made the difference - or close the seacock, take pipe off the engine and backfill the pump.
Impellers can sometimes rotate (or not!) on their central bush - look fine without the cover but stall when you're not looking.

 

[smth448]

I would add another vote for the bypass pipe. Had exactly the same problem and found that was completely blocked with small shells. No idea how they got there!

 

[Impaler]

Thanks everybody, back onboard tomorrow....