Tony Brooks

WE did it in May-June time and the pound with the really low bridge was 50mm down then but we goi to the end. Very pretty, especially with the rhodies and irises.

How about the likes off Bars seal in the Alde header tank. Other car radiator sealers available.

It is almost certain that the leak indicates a worn pump body and shaft. Using the front greaser often seals it enough to get the pump priming but then during use the grease is dispensed so the pump sucks air. BUT most if not all narrow boats will have the pump well below the water level so I don't think this is the problem in this case. It is a question of how much water comes from the exhaust when this happens compared with when the engine is hot and working but not overheating. You mentioned steam and on that sort of cooling system usually (but not always) indicates a loss or reduction in raw water flow. Try not to disturb the rubber O rings when you take the exchanger end cap off, leave them stuck between the core and the main body if you can. With this sort of thing it is often more satisfactory if a knowledgable member can have a look at the boat and tell us exactly what is going on and what you have/how its plumbed. I can well understand you may not want to broadcast you exact location on the internet but giving us some idea of the area may get you help. If you are within 20 miles or so of Reading I would be happy to have a look FOC and suspect MtB would as well.

Since David Mack's post I have been trying to remember exactly how those heat exchangers are constructed and think there core may be in a sort of cast in tube so the base of it, through the filler cap, may well not show the tubes and probing as you suggest will not do any good either as the probe will just scrape the outside of the "tube". As I said I don't see how the end caps can seal without a tube stack. I think there should be a large engine coolant inlet on the bottom of the unit towards one end that leads into the stack space and then and an inlet from the main volume of the header tank at the other ends so coolant is forced to travel the full length of the stack.

Yes, I fear a high lever "Vetus" style one that are prone to leaking air into the system and stopping or reducing the raw water flow.

As you have only posted an image there are no specifications or approvals (ANAYB?) so how can we say if it is any good. What you have to watch is the maximum current it is designed to stand under fault conditions. This can be thousands of amps for a very short while.

A very common fault on older pumps but not usually intermittent but possibly power/speed dependant. Often the early signs is a refusal to self prime without a few more revs. However because of the number of pump types fitted this particular pump back plate may be one that uses a rear shaft bearing and on those the back plate is not reversible because it has a "nose" sticking backwards with a grease cap on it. Any raw water pumps fitted with grease caps (can't see enough of this one) run the shaft in the pump body itself (plain bearing) and these are subject to wear in the body that gain prevents the pump priming but again not usually intermittent. All these pumps I have seen have a mini-stern gland where the shaft exits the pump and when the body is worn fitting new packing can hide the problem for a short while.

That is different and I agree. An easy check to ensure the core is in the case but knowing those heat exchangers I don't know how the O rings will seal without the core ends to keep them in place. The O rind is thin for its size and sits around the core end in a slight taper machined into the end of the body and then the end cap pushes up against it. Without a core the ring would just push away into the body. There is no sign of a gasket or sealer in the photos. The pulley in the first photo drives the raw water pump but there are three pump sizes - heat exchanger engines us the largest one - and one pipe usually comes from the raw water intake or gearbox oil cooler while the other goes to one of the connections on the neat exchanger end cap. The hoses on that cap look far larger than normal to me.

That is not what the OP meant. Raw water passes through the tubes so debris collect at the inlet side of the tubes. This will be under half of the end cap with the big hoses on it. Looking at the outside of the tubes proves nothing. On salty water boats they sometimes have to "rod through" each tube but I have not had to do it on inland craft.

I agree about the location of the thermostat. But Vicki says "The boat runs fine for about half an hour (until the calorifier has heated the hot water tank?), then the temp gauge invariably starts to creep up accompanied by an increasing amount of steam from the exhaust. Running the hot water tap sometimes brings the temperature back down temporarily. " That does not suggest a thermostat jammed shut to me but does suggest a loss of raw water. I think that we can ignore the running the hot water off part because that would provide additional cooling to the engine until the calorifier stops taking heat from the engine coolant. The question is "why is sufficient raw water flow lost". To diagnose much further requires far more info than we have like what is the raw water intake. If this has only stared since leaf faThe boat runs fine for about half an hour (until the calorifier has heated the hot water tank?), then the temp gauge invariably starts to creep up accompanied by an increasing amount of steam from the exhaust. Running the hot water tap sometimes brings the temperature back down temporarily. ll then I suspect leaves (or bread wrappers etc.) being sucked over the intake hole/fitting. Note she gives no indication about the quantity of water coming from the exhaust when the problem occurs. Because of he increase in steam I suspect the water flowing form the exhaust is reduced and if so that would be more indicative of a raw water failure than the thermostat. We also have no info about the speed and power being produced when this happens. As I said de-laminating exhaust hose can cause the symptoms and at first it only tends to happen at higher speeds and powers. As long as the two large O rings under the heat exchanger end caps will still seal it will not hurt to inspect the core for blockages but I would expect that not to cause an intermittent fault. The area that will collect debris is under the cover that has the two hoses in the photo attached to it. The two large hoses SHOULD only be carrying raw water so as long as the inlet tap is turned off no they will self drain when the end cap is removed. Unfortunately there is a long brass rod fixed in that end cap and its is secured by the nut on the other end cap. If care is taken to minimise the disturbance of the O rings there is no need to drain the engine coolant. Some will leak out but the maximum will be the heat exchanger full because its above engine head level. If it is speed and power related then maybe the Jabsco (brass raw water pump) impeller has broken or badly worn teeth so its pumping enough at low speeds to cool but not enough at high speed.

As far as I can see the whole thing is a bodge and have a horrible feeling its a very old heat exchanger indirect raw water cooled engine that has been converted to run on a skin tank. The heat exchanger (the thing across the engine and held on with three nuts) should have one large diameter hose running from the main body to the automotive type engine water pump and the two thinner ones on the end plate. One comping from the raw water pump ad the other going to the manifold and from there into the exhaust. I can't see the raw water pump sufficiently to determine the hose run or if it is large enough for the job and there is a hint it might be feeding water to the calorifier coil. However the talk of steam from the exhaust suggests this is an indirect raw water cooled system and the overheating may well be caused by a blocked raw water inlet, failing raw water pump etc. A delaminating exhaust hose can also cause temporary overheating at higher speeds. I would be very reluctant to suggest that you should even be thinking about a thermostat fault at this time, raw water failure is much more likely so make sure the raw water inlet/strainer id always clear with lots of water coming from the exhaust.

Out of interest I have had the odd Snapon tool fail. The set I bought for the boat came fromHalfords in a sale. We used Halfords tools at College because they lasted, were less "attractive" and lasted very well for the cost.

1. 1/4" sq Drive is ideal for small sockets for things like jubilee clips and 3/8 for most things on the engine but a few things may require the leverage afforded by a 1/2 set. I bought a fairly cheap combination set with 1/4 and 3/8 drive for the boat but then I have my "now not so professional" tools to fall back on when a 1/2 drive was needed. The only thing I think I used it for was the internal anode holder but not so many inland engines have those. 2. just keep them well charged in my view, you are not in the Arctic.

Where is graphite on the galvanic scale compared with mild steel, stainless steel, brass and aluminium? I suspect that may explain why graphite packing might not be ideal but can't see it mattering so much in fresh water.

Quiet correct. A boat designed to cross the Atlantic by the naval architect owner that just happened to be dimensioned to fit the UK narrow canal system.