Yanmar running backwards!

[amadeus]

My trusty 1GM10 had a strange fit at the end of last season and ran backwards, in that it started fine and ran reasonably smoothly in neutral but air was being sucked IN through the exhaust and grey smoke was coming OUT through the air filter into the engine compartment. I thought the boat was on fire!

I turn the engine off immediately, waited ten minutes for the smoke to clear then cautiously fired it up. All went well and it didn't happen again until this week. The mechanic was starting it to check the injector for me and it happened again.

Why is this happening? Engine is 18 years old and very reliable. Could it be a timing issue or a faulty starter motor? Has anyone else managed to do this?

Thanks for input!

 

[dt4134]

It's possessed! you need an Exorcist!

 

[FWB]

It's a known problem with the 1GM10.
A Google search will help. Start here maybe.........

http://www.cruisersforum.com/forums/f54/yanmar-10hp-diesel-runs-backwards-32266.html

 

[andygc]

Amadeus. You will have ruined the foam air filter, so need to get a new one before any more bits go down the air intake. If the cranking speed is low it can bounce back when the fuel ignites - the only time I managed to hand start mine it ran backwards.

 

[Sire]

It doesn't need the starter to be turning the wrong way (will the inertia sort actually work backwards anyway?).

Years ago I had an ancient ERF with a Gardner 100 that would do this - if you stopped cranking at the critical point, the motor could rebound off TDC and, very very rarely, happen to catch and fire up backwards.

Lo and behold! Ten reverse gears and two forwards!

I thought it was an old wives' tale until it happened to me.

 

[dt4134]

Lo and behold! Ten reverse gears and two forwards!

Time to roll out the old Italian tank jokes.

 

[steve28]

get the starter checked and cleaned, check battery voltage is correct to ensure a cell hasnt gone down, tappet gaps .

make sure the air filter is removed until this is sorted as they are expensive unless you make a new one.

Steve

 

[sailorman]

It doesn't need the starter to be turning the wrong way (will the inertia sort actually work backwards anyway?).

Years ago I had an ancient ERF with a Gardner 100 that would do this - if you stopped cranking at the critical point, the motor could rebound off TDC and, very very rarely, happen to catch and fire up backwards.

Lo and behold! Ten reverse gears and two forwards!

I thought it was an old wives' tale until it happened to me.

the very same with the old Thwaites single cylinder dumpers
3 back one forward

 

[agurney]

I've had it a couple of times over the years, usually when the battery was fairly low and I was spinning it up with the compression lever off. If the engine wasn't turning fast enough it bounced but started in reverse.

No lasting ill-effects that I'm aware of. I suppose it means the compressions's reasonable.

Alisdair

 

[amadeus]

Thanks I'll take off the air filter until it is sorted out. I usually rinse the sponge lining through most years to clean it.

 

[ostell]

This happened to someone in my club. New battery was all that was required. One cell that was defective.

Not quite enough urge to get the engine spinning fast enough and bounced backwards from compression.

 

[Kurrawong_Kid]

Join the big ship club! That's how many reverse as does the mighty Dolphin.

 

[fluffc]

I used to use one that started backwards occasionally - but only if you were hand starting it, and didn't give it plenty of 'oomph'

 

[rotrax]

My trusty 1GM10 had a strange fit at the end of last season and ran backwards, in that it started fine and ran reasonably smoothly in neutral but air was being sucked IN through the exhaust and grey smoke was coming OUT through the air filter into the engine compartment. I thought the boat was on fire!

I turn the engine off immediately, waited ten minutes for the smoke to clear then cautiously fired it up. All went well and it didn't happen again until this week. The mechanic was starting it to check the injector for me and it happened again.

Why is this happening? Engine is 18 years old and very reliable. Could it be a timing issue or a faulty starter motor? Has anyone else managed to do this?

Thanks for input!

Hi,The many posters who have said you will be unlikely to suffer permanent damage are correct.Most two stroke engines can run backwards-in fact the messershmit three wheeler with the 250 Sachs engine used a set of points in a different place on the backplate to alter the timing and so achive this.I was running a vintage Scott motorcycle once when it "hiccupped" at some traffic lights.It nearly stopped,but not quite.When I pulled away it shot backwards into the car behind! Proper chrome bumpers on the car and a high rear mudguard on the Scott stopped any damage but it caught my attention! The Yanmar is,of course,a four stroke diesel but ,as you have found it can happen.It would do the engine no good at all if water got into the combustion chamber from the exhaust.I see this as being the worst case.As has been said,a good cranking speed normaly avoids this happening.I always started mine with the decompressor lifted for the first start of the day-get it spinning as fast as it will go and release the decomp. lever-should help.Good luck,Rotrax.