Overheating

[Murv]

Hi Murv

Glad to see your getting to grips with owning an older boat

In reply to others 50/50 antifreeze mix is fine just don't mix types ie longlife and normal

On mud like you I prefer a straight though skin fitting as this can be rodded clear if need be, I used to find a good sharp blow down the pipe clear most things but as you said the Medway can contain all manner of things

ASAP for pump spares, as Omega said regarding cam, broken cover screws usually com out easy enough with pliers.

Thanks for that TallTim.
I must admit I only recently discovered the different types of antifreeze, and the dangers of mixing them. But, it's all long life in there, so I'm happy with the choice of coolant.
The plot actually thickens slightly re the broken cam plate, Superheat6K has very kindly offered to drill and tap the unit for me if I can source the parts. He also sent me a very useful PDF which mentions damage to pumps, like mine has, caused by cavitation through insufficient water pick up. So, it may need a scoop of some description anyway! Maybe there is a design that will cope with the Medway's finest, but I drew a blank at the two local large chandlers.
I will update with any progress!

 

[Davegriff]

"Quote Originally Posted by Davegriff View Post
Probably way off here, but I just noticed that you have a 50:50 antifreeze mix. Antifreeze is not as good a coolant as water - you could be loosing a possible 10-20% cooling capacity over a straight water (no anti freeze, not recommended) coolant at high revs. Could matter if system is already on its limits."


mmmm you sure about that?

Yup.

 

[david_bagshaw]

Yup.

+1

Over concentration of anti freeze, leads to engine failure due to hot spots, commonly in the small galleries around the exhaust valve, leading to failed valves, cracks etc . Seen it personally when I helped out with a local racing team. These guys were using antifreeze neat, & suffered a number of failures.

 

[Murv]

Now sorted, many thanks all.
The water pump was refitted Saturday afternoon at which point the tide promptly went out so couldn't even see if it was water tight.
So...quick test run on Sunday and got a maximum exhaust temperature of 25degC at 4000rpm. Only had time for a couple of two minute blasts, but it overheated rapidly before on the same test so it's looking very promising.

 

[omega2]

If you reckon you have solved the problem try this, after running up the engine grab a hold of the jabsco pump it should be stone cold.

 

[Murv]

If you reckon you have solved the problem try this, after running up the engine grab a hold of the jabsco pump it should be stone cold.

It is
My exhaust sits under the waterline, so I couldn't even tell if the pump was working when I refitted it. Easiest way to tell was with the IR thermometer, the pump and CAC were cold all the way through.

 

[omega2]

It is
My exhaust sits under the waterline, so I couldn't even tell if the pump was working when I refitted it. Easiest way to tell was with the IR thermometer, the pump and CAC were cold all the way through.

sounds good!!

 

[Murv]

So... Tubestack finally removed from the heat exchanger (had to change the turbo gasket which requires removal of the HE) and it looks clean. Except for some strange antifreeze crystallization on some of the rods. So, pressure tested it and, of course, the thing is leaking...
So that's two tubestacks out of the three that have failed now, there's not a chance in hell that I'm ever going to investigate the oil cooler one...


Boats. Why on Earth do I do it???

 

[Fred Munchy]

i had an overheating problem on my Volvo engine. It turned out to be a rubber elbow on the raw water system collapsing and stopping the raw water, the engine then overheated. When I reduced speed she went back to normal temp. I change the raw water hoses for reinforced exhaust hoses and have had no more trouble. Hope this helps.