Mike Adams

I have just pulled the thermostat from my spare(almost new) engine in the workshop which I am sure is factory. Hope this helps. It has a rubber seal at the top. You should see the top open in boiling water or heat it up slowly in a saucepan and you should see it open before the water boils. You can see the quality of the jap oem stat they almost never fail in my experience

Just one thing I forgot to mention and that is there were 2 different versions of the engine and I believe HMI may have used both one is the 4LE1 and the other 4LE2 ,one is direct injection and the other is indirect and although the same capacity use different cylinder heads and May use a different thermostat.

I have a spare engine and will have a look at its thermostat and the weekend but I have a feeling it different to a standard automotive one in that it seals in two places. The cooling system (skin tank)is designed to dissipate at least the maximum waste energy of the engine which is approximately equal to the power output of the engine 40kw. At say tickover the skin tank will take all the waste heat away as it is produced and the engine should only get slightly warm and it will maintain this equilibrium indefinitely. It is extremely important to have the correct thermostat on a modern engine as it is designed both to reach and maintain the correct temperature and maintain thermal balance across the engine and avoid any thermal stress. Running without a thermostat in my opinion could cause head gasket failure and worse. Do you still have the old thermostat ? if so check if it has a rubber ring seal at the base.

If you run it without a thermostat nothing will get hot. If you are going to take the current one out just bung in a new one whilst you are at it. For some reason the thermostats for the 4LE1 are very expensive which makes me think they are slightly different. Try contacting Engines Plus who still supply the industrial version of the engine. I have attached the page of the manual in case you don't have it

Great decision to buy a sea otter which is the boat I should have bought in my old age. I have the problem that I like to fiddle upgrade and mess around with things,sort of part of boating. We have an NT mooring above Pyrford Lock and it is a very nice location. The Wey is one of the nicest waterways now.

Classic example of a stuck open thermostat or damaged water pump impeller. Did you use a genuine part? There is a lot of dodgy Chinese stuff out there.

The calorifier should have two fittings,inlet and outlet, vertically above each other with the coil in between so the highest point is the higher of the two connections unless any pipe connecting to the engine is at a higher level so I would loosen the higher connection to release any air. I think that the temperature sensor is in the thermostat housing as shown in your picture and not on the cylinder head which means it might not be reading correctly the actual engine head temperature. I am not at the boat so I might be wrong on this there may be two switches one for the overheat warning lamp and one for the gauge sensor depending if you have a temperature gauge or not. I think it is unlikely but possible that calorifier loop is blocked but can be checked by disconnecting the engine connections and running a hose though it. hope this helps.

I have found with this engine and my set up (with the calorifier higher than the engine) that even after the engine cools down it maintains some pressure in the system and you can bleed the calorifier from the highest point in the loop even when cold. I fitted a central heating type bleed screw. As you have probably read these engines are often subject to head gasket failure caused by over heating on skin tank cooled models so you really don’t want any air or air locked in the system or you could end up in big trouble. By squeezing the hose From the header tank to the thermostat you can help to get any air out. Make sure you have the correct thermostat installed correctly some can be put in upside down.

Although I've been boating for a mere 54 years I have never understood the concept of living on a boat full time unless it was due to financial hardship. I still really enjoy boating but unless you can afford a large boat such as a dutch barge and a freehold mooring you are at the behest of who ever is the mooring operator and are living in a very cramped space. I have never liked mooring in a marina and have only ever done it on transit and it seems more like a car park to me and most of the time you are just looking at someone else's windows. You would probably be much better off buying a park home in a very nice part of the country where you have at least some security and hiring a boat for couple of weeks out of season. Marinas are often off the beaten track without shops and good bus services so you are reliant on driving.

Unless you can get all the bitumen off, and this can only be done by blasting, then I would just use a single pack bitumen type paint. You cannot get the surface clean enough by any other method and you are very temperature and weather dependant. A few coats of bitumen after pressure washing will last 2 or 3 years and save up your money for a decent professional blast and epoxy in controlled conditions and a lot of physical grief.

Unless you enjoy the process of renovation for its own sake and treat the renovation as a hobby that costs money in the process forget it. I have done 6 renovations in 50 years of boating and enjoyed every one including their use when finished but it has seldom made any return once you factor in your time and materials and tools. you also need a broad skill set to make decent job. It also seems to me that materials and equipment costs are currently very high and any boat that requires substantial renovation, with the exception of some historic vessels, is likely to be problematic in the hull/structure in which case you are wasting your time completely.

But then it did have a proper ice breaking bow. I think crashing around the Paddington Arm these days with several inches of ice would result in a problem for at least some of the towpath residents. That picture must date back to the 30's or 40's and I have never seen it before.

Sorry you have had so much trouble. The one on eBay should have fitted but £92 is ridiculous. I have a complete new engine at home in case anything went wrong with mine but I haven’t needed anything so far. They were fitted to RAF portable nitrogen generators. They come up for sale sometimes. My spare engine had done 20 hours from new and cost a grand so I will swap it over if the current one gets tired. Hope you get it sorted!

This is the Isuzu part number if you need it - Isuzu 897211-2090

I believe this is the correct thermostat for the engine https://www.ebay.co.uk/itm/161514783034?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=W_-gae0XQoC&sssrc=2047675&ssuid=RODum4coRz-&widget_ver=artemis&media=COPY

I should think enginesplus should be able to provide them all as the gasket and thermostat would be standard isuzu parts and they are the distributor.

While a paper gasket may work I would get a new thermostat, composite gasket and pressure cap while you are doing it. For the small cost of these parts its not worth the chance of overheating the engine. That might well warp the head and/or the block on these engines.

The expansion/recovery tank can either be pressurised on not. Most decent vehicles dont have the expansion tank under pressure ie Toyota Landcruiser but then I am biased!

My understanding is that it makes no difference as either allow air to escape during expansion and only liquid to return to the system. However you need the correct type of pressure cap that allows the vacuum created while cooling to draw from the recovery tank and not the atmosphere so it needs to be sealed above the side vent pipe leading to the recovery tank.

My mistake I assumed your coolant bottle pipe enters at the top like mine whereas yours goes in at the bottom. Mine is sat on the floor next to engine.

I think it was 10HP at 1000rpm which was the admiralty spec but you could raise the governor a bit. The 1:1 gearbox would only swing something like a 16 inch prop and that was fine on a 40foot 18 inch draft boat but maybe with an external 3:1 gearbox it might drive a full length boat slowly.

I just had another thought -does your expansion bottle include an internal pipe going to the bottom of the container. If that is missing or broken then the engine cannot draw water back from the expansion bottle as it cools down.

I think the correct one is still available from the successor suppliers at https://www.enginesplus.co.uk/product/water-filler-cap/ The water wont come out until it reaches the top of the mannicooler so warm it up and see if reaches the top when hot. undo the cap very slowly and use a cloth/gloves to prevent any hot water getting on your hands.

When the engine is cold what is the coolant level in the mannicooler? Mine is always full to the brim when I check it which I tend to do every morning. If it not full it probably wont push fluid into the expansion tank. You may have two distinct problems' firstly the small leak. The castings of the mannicooler and thermostat housing may well have been made for HMI the marinisers and not great at not corroding. There are signs of anitfreeze leaking from the thermostat housing on your pictures. This problem should be easily solved by removing the housing and cleaning it up with a new gasket and/or hose and previously discussed. Secondly the pressure build up. My system has quite a lot of hose in it and this expands under pressure it will hold pressure until you release it like deflating an inner tube. I suggest you sort out the first problem and maybe get a new radiator cap and fill the system up and run the engine. This will ensure the cap is letting by at the right pressure in both directions. Hose leaks don't often show up until the system is under pressure so this maybe the cause of the steam. Hope this helps!

Most of the Dorman engines fitted to Ruston Cranes were I think the 2lb to 3ld series which were a nice engine but more modern and powerful than the DSM. I fitted one in White Heather for a time and it was a great engine but unfortunately too heavy for its location in the boat so I had to take it out again! The crane/generator engines appear quite often on ebay.