Bukh DV24 Won’t always turn?

[Mike the Finn]

Hi I’m new here and need some good advice. I bought a used -99 DV24 for my Calypso 720. The engine turned over fine but didn’t start. After a couple more attempts, it seized and we didn’t get it to turn anymore. We tried turning it decompressed and with the nozzles removed. We also swapped a (working) DV20 starter engine on it and checked all the batteries. At this point we gave up after a long day of work. The engine sat untouched for seven days and then suddenly turned over again when I went to turn the key just for fun. The darned thing started on the third try and ran for about five seconds, then stopped and now it’s seized again. So now I’m back to square one and have no idea what’s going on. Any ideas? Thanks in advance.

 

[VicS]

When you say it is seized do you mean you cannot turn it by hand, even if decompressed, or do you just mean it wont turn on the starter motor.

 

[LittleSister]

More detailed info needed to aid analysis.

But while you're at it, do be wary of water ingress into the engine via the exhaust if you are repeatedly turning over the engine without it starting. (The water is pumped into the exhaust when the engine's turned over, but if the engine's not firing it won't be expelled by the exhaust gasses, and can fill the exhaust system and flow back into the cylinders Keith potentially disastrous results. Disconnect the raw water intake pipe if you need to keep turning over the engine without it starting.

 

[Mike the Finn]

When you say it is seized do you mean you cannot turn it by hand, even if decompressed, or do you just mean it wont turn on the starter motor.

Hi, I can’t turn it by hand or starter.

 

[Boater Sam]

Its hydraulically locked do to water in the cylinders. Sort it quick or it will be scrap.

 

[Mike the Finn]

More detailed info needed to aid analysis.

But while you're at it, do be wary of water ingress into the engine via the exhaust if you are repeatedly turning over the engine without it starting. (The water is pumped into the exhaust when the engine's turned over, but if the engine's not firing it won't be expelled by the exhaust gasses, and can fill the exhaust system and flow back into the cylinders Keith potentially disastrous results. Disconnect the raw water intake pipe if you need to keep turning over the engine without it starting.

Hi, here's some more info. So I gambled a bit with the new engine. The owner (a farmer) couldn't tell me much about it, just that he got it as salary for a job that he did. He wanted 600€ for it so I decided to take the risk. I turned it over with a crowbar before I bought it, and I also checked the engine oil from the dipstick and filter and it looked fine (no water). There was some condensation visible underneath the oil cap, but nothing crazy. There is a chance that it's been sitting in someone's garage for years. The engine is a RME so I took the raw water pump, cooling pipe (that goes into the block), and the thermostat from my old DV20. Everything fit perfectly and the engine turned over with the DV20 water pump. The fuel return pipe was missing so I made one with some fuelline laying around. Could this be an issue (bad flow/ too much diesel in the cylinder)?. But the odd thing is that how can it unseize itself with time? Thanks for helping. EDIT: The boat is on dry land and I've tried to start it without cooling water.

 

[Mike the Finn]

Its hydraulically locked do to water in the cylinders. Sort it quick or it will be scrap.

Hi Boater Sam. Could this be because of condensation? I have a feeling that it's been sitting for a long time.

 

[Mike the Finn]

Hi, here's some more info. So I gambled a bit with the new engine. The owner (a farmer) couldn't tell me much about it, just that he got it as salary for a job that he did. He wanted 600€ for it so I decided to take the risk. I turned it over with a crowbar before I bought it, and I also checked the engine oil from the dipstick and filter and it looked fine (no water). There was some condensation visible underneath the oil cap, but nothing crazy. There is a chance that it's been sitting in some one's garages for years. The engine is a RME so I took the raw water pump, cooling pipe (that goes into the block) and the thermostat from my old DV20. Everything fit perfectly and the engine turned over with the DV20 water pump. The fuel return pipe was missing so I made one with some fuelline laying around. Could this be an issue (bad flow/ too much diesel in the cylinder)?. But the odd thing is that how can it unseize it self with time? Thanks for helping.

Oh and one thing to add. Before it got stuck again, I turned over the engine decompressed for a pretty long time (20 sec or so) with the starter motor. So the pistons were free at this point. If this is an issue with water in the cylinders, is it possible to turn the engine decompressed?

 

[penfold]

Yes it would be.

 

[VicS]

So, it can't be hydrolocked . Initially it turned freely so pistons not rusted into the cylinders.
A little worrying that it stopped after a few seconds but that could have been for some trivial reason, air in fuel for example.
Now it won't turn.
I think I'd take another look at the starter motor. Loosen it and give it a wiggle or take it off and see if you can then turn the decompressed engine by hand. (I have a slightly similar problem with a "cherished" car that I cannot explain and have not fully investigated.)

 

[Mike the Finn]

Update: The engine was unstuck again and I could turn it over decompressed very easily by hand. So I tried to start it and it seized up as expected. I removed the head and everything seemed okay, no rust or water. The pistons move about a millimeter with the starter motor and it looks like it’s harder for the pistons to move up than down. So it seems that I have a bigger problem. I’m going to take out the raw water pump (the old dv20 pump) just be sure that it’s not causing any problems (feels unlikely). The next step then will be to lift out the motor again and open it up.

 

[PeterWright]

What is the condition of the flywheel ring gear with which the starter motor pinion engages? It saama quite possible to me that it's badly worn so that some attempts at starting result in the pinion jamming on the ring gear locking the whole engine. Next time it "seizes", loosen the starter motor mounting bolts and wobble the starter motor - if that frees the engine so it can be turned, you've found the problem.
Fairly big strip down to replace the ring gear.

Peter.