Running a 2-stroke outboard dry before storing ?

[Boo2]

Hi,

The instructions for my outboard (Tohatsu 3.5B 2-stroke) say that the fuel cock and tank vent need to be closed before putting it away, and that the float chanmer can be drained if it will be in storage for a while.

I just wondered whether there is any advantage in running the engine dry before storing it by closing the fuel cock while it is running until it stops ? My reason for asking is because I think I may have an issue with crud in the carb and want to prevent its recurrence after I get round to cleaning it.

Thanks,

Boo2

 

[KristiferColumbus]

Hi,

The instructions for my outboard (Tohatsu 3.5B 2-stroke) say that the fuel cock and tank vent need to be closed before putting it away, and that the float chanmer can be drained if it will be in storage for a while.

I just wondered whether there is any advantage in running the engine dry before storing it by closing the fuel cock while it is running until it stops ? My reason for asking is because I think I may have an issue with crud in the carb and want to prevent its recurrence after I get round to cleaning it.

Thanks,

Boo2

If you've got crud in the carb it's because you have got crud in the tank.Both should be cleaned.That dos'nt mean you should run it dry unless you want no oil to protect the engine while it's stored.
Not a good idea unless you want much more serious problems.

 

[Appledore]

Have the same outboard, and I always drain the carb, which (they say) will prevent fuel evaporation and therefore any oily deposits hardening and blocking the jets. And I always invert the engine to empty the fuel from the tank, re-filling it at the start of the season with fresh fuel.

Geoff

 

[JumbleDuck]

I just wondered whether there is any advantage in running the engine dry before storing it by closing the fuel cock while it is running until it stops ?

Or to put it another way, "Would it be a good idea to run my outboard without any lubrication for a bit every time I turn it off?"

 

[NormanS]

I have always run my outboards dry. If you leave "petroil" in the carburettor for any time, the petrol will evaporate, so the next time you try to start, the mix will have too much oil in it, and it may be more difficult to start.
It doesn't really mean running the engine without any lubrication. It's only on tick-over, and will stop as soon as there's no petrol ( and oil) left.

 

[Appledore]

This is from page 45 of the User Manual:

③
Drain all fuel from the fuel hoses,
and carburetor, and clean these
parts.
Keep in mind that if gasoline
is kept in the carburetor for a
long time, gum and varnish will
develop, causing the float valve to
stick, restricting the fuel flow

 

[Stemar]

Interesting comments.

The other way of looking at it is, "Would it be a good idea to leave oil and fuel in the carburettor jets so it can evaporate to sludge when the engine's in storage?"

I'm no expert but AFAIK, the splash lubrication of a 2T motor leaves everything coated with oil as the atomised fuel passes through the crank case. I really can't see how the second or two with no fresh oil will make any difference.

I've flushed my Tohatsu 3.5 in fresh water and run it dry before putting it away for the last 13 years and it's still going strong.

 

[VicS]

Hi,

The instructions for my outboard (Tohatsu 3.5B 2-stroke) say that the fuel cock and tank vent need to be closed before putting it away, and that the float chanmer can be drained if it will be in storage for a while.

I just wondered whether there is any advantage in running the engine dry before storing it by closing the fuel cock while it is running until it stops ? My reason for asking is because I think I may have an issue with crud in the carb and want to prevent its recurrence after I get round to cleaning it.

Thanks,

Boo2

Or to put it another way, "Would it be a good idea to run my outboard without any lubrication for a bit every time I turn it off?"

Running the engine until it stops is not likely to run the carb completely dry so the advice to drain the float chamber is still just as valid. ( If its valid at all)

JD's objections are perhaps valid for a 100:1 motor but a 50:1 motor is well oiled at idle speed and the insides should be adequately coated with oil . No bad idea though to add a little extra oil to the mix before laying up for longer term storage ( certainly do that for a 100:1 motor, no debate)

Better still is to spray in fogging oil until the motor stalls. ( Personally I now, at the suggestion of a local dealer, spray in neat two stroke oil from a trigger spray bottle) That leaves the carb bowl full of course.


FWIW I always run my outboard dry ( as dry as it gets anyway) after normal periods of use but I always fog it before a winter lay up. It does not have a carb darin, not that it would be accessible even if it did. I do not normally therefore drain the carb, or even run it dry, before layups or longer periods of storage. It's 30 years old and as yet I have had no problems whatsoever with the carb. It has not been cleaned or even removed from the engine in all that time.

Absolute cleanliness when handling fuel is IMO the key to a trouble free outboard.

 

[Seajet]

I agree with most of the comments here, don't run the engine dry as that means no lubrication.

When stowing the engine to ' sailing mode ' I briefly disconnect the fuel supply so as to reduce the chances of spilling fuel in the locker, but never run it to stopping point.

Before winter or any long layup I drain the carb - usually easily done with a chubby flat blade screwdriver - and remove the spark plug, liberally spraying in WD40 while turning the engine over.

Seems to work, my Mariner 5hp is decades old now and runs well, the Yamaha 4hp before it and relegated to Plan B spare is an early 1980-'s job and still happy.

I am however quite fussy about fuel, anything left over at the end of the season goes into my non - catalytic ' classic ' car, and onboard I always use a splashproof funnel with a filter.

 

[RichardS]

Running a two stroke with fuel off will not do any harm lubrication wise. The crankcase inners and bore are well-coated with oil and a more limited supply as the fuel runs down is fine as once the fuel throughput starts to become limited the engine is almost ready to stop. Of course, running a 2T on a weak mixture longer term is not advisable as the oil coating will always be insufficient.

However, I would still recommend draining the carb tjhrough the lower drain because any build up of crud in the bowl might well remain in there if you just run the engine dry, ready to cause a problem next season. If you drain the carb you remove the crud and will start the next season with a clean float chamber.

Richard

 

[macd]

+1 with Stemar and Richard S.

Look, guys, if it's running, it must have fuel. And if it has fuel, it must have oil. There's not the remotest possibility of denying the engine oil by switching off the fuel and allowing the carb to run dry.

Anyone who's ever stripped a healthy 2-stroke will know that the innards are always generously coated with a film of beautifully clean oil.

However, as KrisoferColumbus wrote, if there's a suspicion of dirty fuel, clearly this should be investigated and dealt with.

 

[VicS]

Running a two stroke with fuel off will not do any harm lubrication wise. The crankcase inners and bore are well-coated with oil and a more limited supply as the fuel runs down is fine as once the fuel throughput starts to become limited the engine is almost ready to stop.

And once it stops it's not running any more so lubrication is no longer a problem.

Big multiple carb engines are another matter though. The V6 and V8 engines The design of the fuel systems can mean that the carbs on the upper cylinders run out of fuel, and therefore oil, before the lower ones.

i guess however we are talking here about single carb engines

 

[macd]

Big multiple carb engines are another matter though. The V6 and V8 engines The design of the fuel systems can mean that the carbs on the upper cylinders run out of fuel, and therefore oil, before the lower ones.

I've absolutely no knowledge of such engines, Vic, but wouldn't they have a pumped lubrication system? Or do they depend on plain old petroil?

 

[ip485]

Always run my 15HP dry if left unused for more than a few weeks. Touch wood no problems so far. I can see both sides of the discussion. After all the trouble with my four stroke that refused to start after very little time if not run dry and then still often didnt (new engine I might add) the 2 stroke hasnt failed yet - six months last year and started on the third pull.

 

[NormanS]

As I have said already, I always run my little outboard dry. If you are running onto a beach, the engine is going to be tipped up anyway, so fuel left in the float chamber is going to be spilled out, so I try to judge when to switch off the fuel.
Not only am I getting the use of all the fuel, but also saving the world from all that needless pollution.

 

[vyv_cox]

It is quite astonishing how little oil is needed to lubricate bearings. Two inch ball bearings in the tribology lab were run using 5 ml of oil within the bearing, run for hours at 3600 rpm. The oil was then analysed for acidity, particles and various other properties.

I always stop my engine by turning off the fuel about 30 metres before reaching the boat. I find it starts and runs reliably, even after a winter unused.

 

[steve66]

Do not use WD40. Its a degreser. It will wash off any oil you have left in your cylinder then evaporate. If you have to do anything just squirt a little oil into the combustion chamber and pull it over a few times.

I agree with most of the comments here, don't run the engine dry as that means no lubrication.

When stowing the engine to ' sailing mode ' I briefly disconnect the fuel supply so as to reduce the chances of spilling fuel in the locker, but never run it to stopping point.

Before winter or any long layup I drain the carb - usually easily done with a chubby flat blade screwdriver - and remove the spark plug, liberally spraying in WD40 while turning the engine over.

Seems to work, my Mariner 5hp is decades old now and runs well, the Yamaha 4hp before it and relegated to Plan B spare is an early 1980-'s job and still happy.

I am however quite fussy about fuel, anything left over at the end of the season goes into my non - catalytic ' classic ' car, and onboard I always use a splashproof funnel with a filter.

 

[PetiteFleur]

I always run my Suzuki 2.2hp dry by turning off the tap whilst running in the water butt. I don't usually drain the tank and 5 months later I top up with fresh fuel and it always starts 2nd or 3rd pull. When returning to shore I turn off the fuel tap about 50 metres from landing.

 

[VicS]

Do not use WD40. Its a degreser. It will wash off any oil you have left in your cylinder then evaporate. If you have to do anything just squirt a little oil into the combustion chamber and pull it over a few times.

ITYWF It actually contains more light oil than two stroke fuel mixtures That said I'd not use it in the way Seajet suggests. I now use neat 2 stroke oil in a trigger spray bottle in lieu of fogging oil.

 

[david_bagshaw]

+1 with Stemar and Richard S.

Look, guys, if it's running, it must have fuel. And if it has fuel, it must have oil. There's not the remotest possibility of denying the engine oil by switching off the fuel and allowing the carb to run dry.

Anyone who's ever stripped a healthy 2-stroke will know that the innards are always generously coated with a film of beautifully clean oil.

However, as KrisoferColumbus wrote, if there's a suspicion of dirty fuel, clearly this should be investigated and dealt with.

+1

Have injected 2 t oil directly into the carb throat at laying up, along with removing spark plugs and inject into the cylinder. That is with 4 stroke outboards as well. It cant be too bad as the present engine is now 15 years old., and without deposits.