Yanmar 1gm10 starting in reverse!

[tom_sail]

Usually my yanmar 1gm10 starts and runs sweet as a nut.

Today I went to start it and almost immediately the cabin filled with smoke. Quickly shut it down with all 4 fire extinguishers pointed towards the engine compartment.

The air filter was covered in soot along with the sides of the engine compartment.

I later discovered the air was being sucked though the exhaust and blown out the air filter meaning the engine was firing the wrong way

Once the smoke had cleared I had another go and it ran fine even went for a test motoring up the channel.

Firstly, what caused it to to have this moment of madness?
Has it done any damage to the engine?
Possibility of Sea water getting blown back up the exhaust elbow into the cylinder?

Thanks

 

[agurney]

I've had that a couple of times, though it usually stops after the first couple of coughs.

Seems to happen when the battery is low and the flywheel isn't turning fast - it 'bounces' off the compression and catches on the return.

 

[DanTribe]

My 1GM did that to me in the middle of the North Sea some while ago.
We were motoring slowly when the engine stopped dead. I tried to restart but it kicked and ran backwards, as you say, loads of smoke and popping noises, frightened the life out of me. After thorough checking I tried again and it ran fine.
My theory; we picked up a rope which stopped the engine, on first re-start the prop bounced off the rope and kicked the engine backwards, freeing the rope.
Lots of experts laughed and said it's not possible, but it DID happen.

 

[tom_sail]

Glad it's happened before, I remember reading on here before about it happening, I thought it was an April fools.

My cranking battery is a little flat after a week of no use.

Maybe next time I'll start it with the decompression lever up and then drop it.

It's scary how much smoke there was I couldn't see a few feet in front of me

 

[agurney]

Glad it's happened before, I remember reading on here before about it happening, I thought it was an April fools.

My cranking battery is a little flat after a week of no use.

Maybe next time I'll start it with the decompression lever up and then drop it.

It's scary how much smoke there was I couldn't see a few feet in front of me

It's only happened to me been when I've dropped the lever while cranking ..

 

[Ephesian]

I've had the same with our 2gm20 when we tried to hand crank it started (just to see if we could). Spun it up with the handle, dropped the decompression levers and it bounced back and started backwards. Not only exhaust fumes everwhere but also the starting handle spinning around because doesn't disengage properly in that direction...

Took us a while to work out what happened!

After I thought about it I figured it had probably messed up the air filter with exhaust particles, and also would have run the raw water impeller backwards too, so no cooling. I also wondered if it would have sucked water out of the trap in the exhaust if we'd left it running long enough...

We haven't tried hand starting since!

 

[sailorman]

Usually my yanmar 1gm10 starts and runs sweet as a nut.

Today I went to start it and almost immediately the cabin filled with smoke. Quickly shut it down with all 4 fire extinguishers pointed towards the engine compartment.

The air filter was covered in soot along with the sides of the engine compartment.

I later discovered the air was being sucked though the exhaust and blown out the air filter meaning the engine was firing the wrong way

Once the smoke had cleared I had another go and it ran fine even went for a test motoring up the channel.

Firstly, what caused it to to have this moment of madness?
Has it done any damage to the engine?
Possibility of Sea water getting blown back up the exhaust elbow into the cylinder?

Thanks

we used to get that with site dumpers
1 forward
3 reverse

 

[tom_sail]

Thanks for the replies.

I took the boat for a quick motor up the channel and she didn't miss a beat.

I'll have to order a new air filter the other one disintegrated when the exhaust air blew it to pieces. Hopefully none got sucked into the engine.

 

[wiggy]

On my last boat my 1gm10 used to do it quite regularly, I found that starting with no throttle completely eliminated it and improved starting in general.

 

[jfkal]

Wow

Thanks for the replies.

I took the boat for a quick motor up the channel and she didn't miss a beat.

I'll have to order a new air filter the other one disintegrated when the exhaust air blew it to pieces. Hopefully none got sucked into the engine.

Yes the Yanmars are cute little engines. Thought of getting rid of the gear box altogether since they run in both directions.
My 3GM30 (previous engine ) did this also. Quite a mess. Dont worry about the filter bits (actually it is not a filter but a silencer). The Yanmars always "eat" them since they pulverize over time (no ill effects apparently, base engine is for a tractor and they are always eating dirt.). Once the third silencer had disappeared through the engines inner works I gave up and installed an external motor cycle intake filter.
Replace the impeller though as they do not like to get flipped over. (Mine however survived).

 

[tom_sail]

Thanks for Thinking about the impeller that didn't cross my mind!
Also the oil pressure warning light sounded I guess that was because the oil pump was in reverse to.

 

[maby]

It is quite common with single cylinder diesels - our 1gm10 did it quite regularly. It does seem to be related to conditions that make starting difficult - cold weather or low battery. It is nothing to do with ropes round props or anything like that - simply that it has a tendancy to rebound off the compression stroke if you release the starter before it has started firing.

Provided you stop it quickly, there is no damage. As you say, the oil pressure never builds up because the pump is running in reverse so letting it run like that for any period of time would do damage, but you would choke on the exhaust first. On our old boat, the engine stop was a handle in the cockpit locker - too far from the starter for one person to reliably handle both. We had a routine in which my wife stood by on the stop control while I operated the starter.

 

[jfkal]

Oil pressure

Thanks for Thinking about the impeller that didn't cross my mind!
Also the oil pressure warning light sounded I guess that was because the oil pump was in reverse to.

Indeed. I did not hear mine whining as the noise from the 3 cylinder running in reverse was deafening :-0

 

[prv]

On our old boat, the engine stop was a handle in the cockpit locker - too far from the starter for one person to reliably handle both. We had a routine in which my wife stood by on the stop control while I operated the starter.

Mine originally had the starter in the cabin just below the companionway, and the stop handle under the seat at the aft end of the cockpit. No idea what was going through the mind of whoever came up with that one; even without reverse running it meant you had to leap from one end of the cockpit to the other to shut off the annoying buzzer after stopping. During our first season I simply moved the stop to be next to the start; easier than deploying wives . I also added a buzzer-silence switch when I rebuilt the whole panel the following winter.

Pete