Lister SR4 or SL4 diesel
QI have come to the end of my tether with this engine the problem seems to be excessive heat produced when the engine has been running for 30 minutes or so we have even gone down the road of cutting a hole in the roof and putting a duct down from the roof with a large radiator type fan drawing in cool air right above the engines own fan and running with the deck boards off. After a 30 minute run it will not tick over and if it restarts,when you try to rev it up it just doesn’t react but when cold its fine. the engine also has quite a bit of blueish smoke from the exhaust. I must explain that the engine came with the boat and was very tight through water ingress into one cylinder we have removed the slight ring of rust in the bore and the engine has good compression and starts very easily and is now quite free with no signs of the seizure we also did the bump test and set it for the recommended 35thou it has probably run now for about 20 hours and when just ticking over charging batteries will run all day its only when under cruising conditions that it has this problem its as if it runs out of fuel but there is plenty of fuel getting to the injector pump. I am quite knowledgeable with engines but this one has me beat. I hope you can give me some pointers before I go down the road of changing the engine for something more modern.
Mike Darnell Note: to readers – I no longer run such courses
ATONY REPLIES: When an air cooled Lister displays those symptoms my first thoughts would be oil dilution caused by a broken internal fuel pipe or a loose internal union. However that normally has two more symptoms: a rising sump oil level with the oil thinning. In the latter stages when it causes stalling when hot there is usually a smell of diesel around the engine. I note you do not mention those last set of symptoms so if the oil level is constant it can not be that.
If there are no shaped pieces of “tin” with little loops on to slide over the cylinder retaining head studs and pushed down between the cylinders I expect there is a good chance that fitting them will cure the problem. If they are missing I suspect the cylinder furthest from the fan may be overheating and seizing up. These air flow directing plates are vital on multi-cylinder air cooled engines. It is also common for the ducts to be fitted upside down and that again starves cylinders of cooling air. This would be my first check. It is also vital that the hot cooling air expelled from the side of the engine (assuming the outer thin metal cowling is not broken and is in place) isn’t allowed to simply circulate back into the engine room. When a duct broke on our SL4s on the hire fleet we often found the inserts in the piston crown popped out demanding a new piston and sometimes a new con-rod and valves.
If this does not solve the issue talk to Marine Engine Services (Midlands)/ Primrose Engineering who seem to be the inland Lister specialist.