I'm embarrassed to show you this....

Well I have sorted my overheating problems. Now all you engineers and armchair engineers out there cut me some slack on this. I have to diagnose my problems logically but sometimes I think my logic is influenced by the complexity of the job that the problem might generate.

So when the boat overheated I tried a few things first but eventually rounded on the water pump impeller. Not a difficult job but one that meant draining the block down. Suitable armed with the correct part I set to with a small cut down milk bottle container to catch the water as I loosened then closed the water pump cover. This was a slow but precise job that saw no water end up under the engine. About four and a half litres came out before the water stopped. It was a greeny blue tint and using my antifreeze tester it showed not a lot of protection. I took a small bottle off to ensure I filled with the correct type of antifreeze - more later.

Now prepare yourself dear reader for a shocking picture ....  This little thing has just run out of ideas on how to move water for obvious reasons. I did contemplate not showing this pic unless someone asked for it then I'd email it in a brown paper packet !!

Can you spot the old one from the new one ?

I watched a few YouTube Videos about swapping the impeller and mine was by far the best condition!!

My little workshop, cleaning up the faces and plate on the water pump before sending the next little rubber jobbie into battle 

How it should look, all snug and tight.

All put back together and running cool.... in hindsight the engine had been getting warmer over the last few cruises but not overheating.... the donk is now back to supercool again all pipes ding what they should - happy idiot again.

A few observations. 

1. The missing bits will almost certainly be a the bottom of the crud catcher area of the skin tank - a bit like the diesel tank on most boats that have the take off a few inches above the bottom to allow the crap the not be drawn off - my skin tank is designed the same. 

2. Why did it happen - well reading around the issue is seems if the engine is left to stand the rubber binds to the brass and when the engine is started it tears the vanes off the impeller - mine showed just that and is consistent with not starting it. I thought I was being good not running the engine as we had solar and a water heater.... I am now the wiser, the engine will get warmed up once a week from now on.

3. The impeller IS a consumable  - did you know that and when did you lat change yours? Maybe if the engine is running ok and you have a decent regime not to worry but I think now I'll be replacing mine every 2-3 years. The price was around £30 

4. I tested the coolant and it was weak so it enabled me to add in some more antifreeze. To be sure I mixed the new and old in a jar and there was not sludgy reaction (can happen if you mix two types) 

5. The engine did get hot so I am going to get the head gasket replaced. No reason to think it was damaged by the overheat as the engine is a massive slab of cast iron.  It has always had a slight weep out wards so is due and it'll get a check and decoke at the same time. I now know a regarded marine engineer who will do this for me and hopefully I can watch so next time I can do it myself. 

The boat now has a new thermostat and impeller as well as fresh antifreeze so when the head comes off it'll get new oil and maybe even the case opened up to check the inners for wear and clean out the sludge in the sump - if there is any. One of the benefits of an old engine.

So wiser, and not too much lighter in the wallet and the engine runs nice and cool and sound much better with the newer antifreeze in there. 

Once again apologies for the images, only one impeller were harmed in the posting of this update !!