Running a 2-stroke dry after use

[Greenheart]

I inherited a five-gallon remote tank with my Mariner 5hp two-stroke.

My understanding of the instructions for use were very clearly that having arrived, the remote tank should be disconnected while the engine continued to idle, so the remaining fuel in the engine's pipes would be used up, thereby finally stopping the engine and enabling it to be lifted off the bracket and stowed without residual fuel dribbling out.

But I found this morning, the words of a Mr Bane in Practical Boat Owner January 2017, page 47...

"It is common practice, at the end of a day's sailing, to disconnect the fuel line and run the motor until it stops. This helps empty the carburettor. I found out the hard way that if the motor is a two-stroke you should not let it run until it stops, but rather stop it deliberately when it starts to run roughly. This will ensure that there is a coating of fuel and oil in the cylinder, and protect against rust in storage."

...the gist of which seems to fly in the face of earlier instructions. What is the best way?

 

[lw395]

I try to reduce the amount of fuel i nthe carb by turning off the fuel tap a while before stopping the engine.
It's best to use engines regularly, this avoids corrosion issues.
If you're going to 'store' an engine for more than a week or 3, there is always a risk the oil will run off the cylinder walls.
But generally I've always found letting the car run dry leaves oil all over the inside of the engine.
I generally aim at the slipway, turn the fuel off with say 1/3 throttle. There isn't really a 'rough running' phase, it coughs onces, stops and we coast to the slipway.

Long term storage, one should take the plug out and chuck in some oil. And turn the engine over from time to time in storage.

 

[Skylark]

The primary objective is to ensure that there’s no fuel left in the carb as it risks gumming-up the works.

I’ve turned the fuel tap off and let the engine run dry on several engines over many years and not had a problem. I’ll occasionally drain the carb (screw) instead of running it dry if the situation dictates. I always run the engine with fresh water to remove salt. If I’m winterising the engine, among other things, I’ll remove the plug and ensure that it’s well lubricated.

 

[Seajet]

+1, Like what david jackson just said.

 

[davidmh]

Yes run it dry. If I store in over the winter I put a drop or two of two stroke oil on the plug hole and turn it over a couple of times and put the plug back. Always seems to start first pull next season
David MH

 

[anoccasionalyachtsman]

I'd take a wild guess that an engine will stop when the fuel air mix drops to 75% of that normally supplied at idle. And that means that it'll still have 75% of the oil that would have been left if the ignition was cut.

 

[ganter]

Unless leaving it for an extended length of time I really wouldn't fret about it.
2-Strokes are engines designed to be readily in-demand and as such don't give a monkey's about what state they're left in.

Wintering - of course - starve the fuel, dry the carb and let the cylinders plonk out - then, when back in the garage, rinse and repeat that in a wheelie-bin of fresh water to wash out the ports and hey! - you're done!

If you get paranoid about your carb gumming up by some carb cleaner and give it a squirt or two straight in to the air intake followed by another quick squirt of WD40 to line it.

(I use to race 2-Stroke motorbikes in the '80's - very expensive ones.)

 

[LadyInBed]

I've always had 2 strokes and I turn off the fuel to let the carb run dry. One of the two I have is about 40 years old and still performs well. I took the head off a couple of years ago to check the waterways. No rust around the head or bore.

 

[thinwater]

a. The run-out advice from the factory is that this is only required for storage, say, more than a month. I hanve not run and engine dry in 40 years either, and they always start.
b. Disconnecting the fitting after every use is a sure way to wear out the fitting. Just sayin'.
b. Use a good additive, like Biobor EB.

 

[Graham376]

I don't bother running the carb dry and never had a problem even after storing for 3-4 months. When storing, I do flush out with fresh water.

 

[Praxinoscope]

Every time with a Seagull, must have the leakiest carbs in the world, not so bothered with most other 2 strokes.

 

[Seajet]

Certainly in my case it's mainly so it doesn't leak fuel if stowed flat in a locker.

For winter ashore I give both 2 & 5hp a good run in fresh water ( spare wheelie bin ) and run the carbs dry then.

The Mariner / Yamaha 2hp 2-stroke is a fantastic engine but does need attention to prevent the waterways clogging with salt.

 

[SAMYL]

It's a misconception that you can run a carb dry, you can't.
There will always be a level of fuel in the float bowl and this can only be removed by laying the engine on its side and draining it that way.
Unfortunately that leads to the possibility of residual water in the passageways running back into the cylinder causing corrosion there.

 

[Kelpie]

It's a misconception that you can run a carb dry, you can't.
There will always be a level of fuel in the float bowl and this can only be removed by laying the engine on its side and draining it that way.
Unfortunately that leads to the possibility of residual water in the passageways running back into the cylinder causing corrosion there.

Don't most carbs have a drain screw?

 

[Billows]

It's a misconception that you can run a carb dry, you can't.
There will always be a level of fuel in the float bowl and this can only be removed by laying the engine on its side and draining it that way.
Unfortunately that leads to the possibility of residual water in the passageways running back into the cylinder causing corrosion there.

Is it not the fuel in the little passages and jets that cause the problem not residual fuel in the bowl? This is why draining using the bowl drain screw wont help the above

 

[Greenheart]

I'm grateful for the many responses here. Trouble is, I get the feeling I'll have to go through the same period of trial, error, cock-up and component repair/replacement that you've all been through, too.

Is the problem caused by different engines requiring differing procedures? Everybody seems to have a personal way that suits, so until we learn that our way is causing a problem, we claim it works for us, and thereby propagate methods that may not be ideal.

Maybe there's an online guide to two-stroke use, that I can study before blindly causing or exacerbating problems?

Do we think the view of the chap in the PBO article with which I began this thread, is misleading? He didn't go into explanatory detail, but he seemed very sure and presumably the editor concurred.

 

[Graham376]

Maybe there's an online guide to two-stroke use, that I can study before blindly causing or exacerbating problems?

If in doubt follow the manufacturer's handbook instructions, particularly while still under warranty.

 

[Greenheart]

Thanks, but I reckon a very small minority of two-strokes in the UK will still be under warranty.

Mine's around 15 years old and I've no knowledge of its provenance.

I believe the manual may be recoverable online...someone on here showed me where, lately...I'll find the handy link which I think covered hundreds of engines.

 

[RichardS]

Is it not the fuel in the little passages and jets that cause the problem not residual fuel in the bowl? This is why draining using the bowl drain screw wont help the above

It is the fuel in the carb bowl which dries out and causes the problem. Eventually it leaves a sticky gummy residue which can them find it's way into the jets when the engine is re-fuelled and start to cause problems. The only way to properly drain the carb is via the carb drain, assuming one is fitted, although I agree that running the engine until it stops is better than just leaving the bowl full of 2T mix. It won't do the engine any harm as long as it's only idling to a stop.

Richard

 

[thinwater]

Run every day, few would run the carb dry. I think there are several obvious ways in which this can be slightly damamging, and it is certainly pointless. Same for once a week. Seasonal storage is pretty clear; the carb should be drained. The OEMs say so. It is the middle ground that is confusing.

If the engine is going to run once every 2-6 weeks, which is more likely to generate gum?

a. A carb left full. It may evaporate down ~ 1/4, and then be rinsed clean when it is refilled. The carb will not evaporate dry in so little time. I've pulled enough carbs to be sure of that. I've also run many tests with carbs to research evap rates. It takes >2 months in the heat of the summer. Gasoline does NOT evaporate to dryness that quickly.
b. A carb run dry, which probably still contains < 1/4 of its fuel and will probably dry out.

These numbers could be wrong, but not all wrong.

I've searched many manuals and spoken with senior engineering staff with several OEMs. They all say draining is for extended (more than 3 months) only. However, if there is something from an OEM on the net PLEASE post it!! I would love to see specific, written OEM guidance.