Strange thing happened today

[David M]

Waterlock could be eliminated by turning it backwards. Remember that the valves are aligned to let air in until it reaches the compression stage. Therefore water at the compression stage, now run backwards would allow for the water to escape to the intake manifold.

[Dave_S]

It is probable that after turning it backwards that there was still more than a combustion chamber full of liquid and may have done some damage.

When you did start it it may have had a little trouble turning over the first revolution if so there may be some damage. If it turned over without any hesitation then it may be fine.

The other options given by others above are also possible but it sounds like water in the cylinder to me.

[seabreez]

Originally Posted by Gulf Islander

This was a first for me. Tried to start my diesel and it would make a quarter turn and then stop. Big Clunk. Tried it again and same thing. I then grabbed a pipe wrench and turned the crank quarter turn then stop. I scratched my head and then decided to reverse crank and it was free. It was all of a sudden it was free. I started the engine and it has been running for the last 3hrs just fine. What could have cause this.

I had this happen on a GM 4-71 and it was water in the cylinder. When turning in reverse the water went out in the exhaust port and in the muffler and of course when you started the motor the water blew out the exhaust. Be careful on the next start up it might do it again. Where the water came from is the mystery. The water can come in by the exhaust by the muffler and can come in through the intake... rain water or it can come in by a leaking cylinder head gasket. Ours never did it again so I ass-u-me it came in by the exhaust... let me know if this happens again and I will walk you through to try and find out by process of elimination.

[SULAIRE123]

Originally Posted by Gulf Islander

This was a first for me. Tried to start my diesel and it would make a quarter turn and then stop. Big Clunk. Tried it again and same thing. I then grabbed a pipe wrench and turned the crank quarter turn then stop. I scratched my head and then decided to reverse crank and it was free. It was all of a sudden it was free. I started the engine and it has been running for the last 3hrs just fine. What could have cause this.

I had similar with Perkins 4.108 with
Hurth mechanical gearbox.
Feared the worst (engine seizing)
Removed gearbox from engine and engine free
It was primary shaft in gearbox seized up
Check gearbox oil level first
Good luck !

[buzzstar]

I do not know, and also watching with interest (senormechanico has an idea or is playing possum?). My immediate thought was a mechanical/physical block at some point (external to engine?) and, as suggested, it dropped away with reverse movement, which made me think, flywheel tooth or starter pawl, or gearbox, or prop as the only likely mechanical leverage suspects. Anyway, I do not know! Hope this will be 'splained in the fullness of time. sort of reminds me of my long ago MG TD (gas) which would every now and again jam on starting. Fortunately, I could use the hand crank to loosen things and start it too.

[brownoarsman]

This happened to me and it was a 'weak hydrolock' caused by backflow from the wet exhaust manifold after the engine had been shut down. Enough water to overwhelm the starter motor, but clearing the cylinder by either reversing the crank or throwing the decompression levers, and hand cranking forward and pushing the water out sorted it.

Hydrolock while the engine is running could have more dire consequences so it's important to distinguish the two.

[GBonjour]

All good but I am thinking a bolt worked out and gets stuck in the flywheel and when it was turned backwards it turned adifferent way and is now just laying out of the way.

[KadeyKrogen38]

A friend with an older Westerbek engine which would hydrolock occasionally would turn the engine over by hand in reverse rotation to clear water.

The engine would start back up reliabily

He would change the old a couple of times and that was it. Engine lasted more than twenty years of regular cruising.

[Gulf Islander]

Westerbeke 4-60

[buzzstar]

I do not know enough to "get it." Does not hydrolock draw water into the cyliners(s)?

[senormechanico]

No possum here, just really interested.
Thankfully, I've never experienced this.

[atoll]

Originally Posted by buzzstar

I do not know enough to "get it." Does not hydrolock draw water into the cyliners(s)?

it is generally caused by the intake raw water siphoning into the exhaust drop box (when the engine is stopped),which fills up,then fills via the exhaust, any cylinder that has an exhaust valve open.
generally on engines that are below the waterline,or by excessive cranking without the engine starting

[daletournier]

It can also come in through water fed dripless shaft seal ,depending on the setup.
Do you have decompression valves? Easiest way to clear hydrolock if thats the issue.
Antisiphon valves salt up, few people check them on a regular basis.

[Hunky Dory]

I had this happen once, and it was more than enough. I had a stuck valve, the piston came up and hit the valve and stopped the piston rotation, The counter rotation freed the valve, and it never did it again. I was lucky the engine didn't start, it could of bent the valve stem or knocked a hole in the piston. Lots of luck.