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Running Carbs Dry Between Uses???

J

John Haggerty

Contributing Member
1989 70hp Johnson

I more often than not run the carbs dry between uses. Of course time between uses is a major factor. I'm currently not working so plan on using the motor at least once a week. I'm curious what most folks do and what is best for the motor. Only recently I've been using Rec 90 fuel. Thoughts?

Thanks,
John
 
I run pretty much every weekend and I never do...
I would say even if you ran once every month you would be fine.
And - even if you ran the motor till it stopped - the carbs still hold a bit of fuel... If you were idle for a few months or more some seafoam in the gas or sta-bil will keep you ready to go till next time.
Just my 2 cents worth...
 
I understand that it it is not advisable to run multiple carb engines dry. The design of the fuel system can mean that the upper carbs run dry first and therefore there is no lubrication of the upper cylinders in the last few moments before the engine stops.
 
the worse thing you can do is something you see often at the landings is run the gas out at high rpm....when i ran carb engine 13-1500 was tops and be prepared to press choke to get the most fuel out..i also think its wise to go ahead and run the gas out even though you plan to use it soon..we were fishing hard one spring long ago...every weekend and long weekends when i could...broke my run out rule and something happened and didnt use the boat(camp boat) for a long time...will say no more....
 
(Running Engine Out Of Gas)
(J. Reeves)

If the engine has but one carburetor, it's unlikely that running the engine out of gas would do any harm. When the carburetor runs out of the fuel/oil mixture, the engine stops running.


However, a engine that has more than one carburetor should simply be shut off. The reasoning is that the top carburetor will run out of fuel first due to gravity and the engine will continue to run on because of the still existing fuel in the other lower carburetors.


This results in having at least one aluminum piston running up and down a steel cylinder wall with improper or no lubrication. Not a good idea!


Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
In order to lubricate oil must be coating the parts.------That oil comes in via the fuel.--------When carburetor runs out of fuel there is lots of oil on the parts and no damage will occur as the cylinder is now cooling and not doing any work.--------The oil just does not disappear in an instant.-------Does anyone here know how long a given droplet of oil stays in the engine before it is burned off ???
 
personally I have always ran the motor out of fuel when putting away.
to say a multi carb engine drains op carb first is not correct at all.
my engine for example is a inline 3cylinder, all 3 carbs pull the juice from small plastic manifold.
now when I pull the fuel line, all 3 carbs are already full. each carb will drain at roughly the same time.
The top cylinder is not always he first to die, mine pretty much just stops.
pistons are still oily to the touch when an engine gets stripped down. But do NOT have throttle any more than just idle.

just my thoughts on this.
.
 
I agree with Racer and Phil.
Run an engine out of gas, pull the head, and you will see all cyls are still well oiled up.
 
When there is just air going through a crankcase how is it possible for oil that is coating the parts to disappear in an instant ??????
 
Progator135...... AW, go ahead and continue to run those carburetors out of gas as suggested by various individuals that disagree with OMC's recommendations. Hell, when that piston or bearing fails and takes along other various internal components, I"m sure they'll be the first in line to offer you all the financial assistance you may require. :cool:
 
There will be no catastrophic failures !!!----OMC may have used this trick to get out of paying for warranty failures !!----Easy to blame an owner who may not know how a 2 stroke actually works.
 
C'mon racerone... you know as well as I do that OMC bent over backwards to take care of warranty failures even when the warranty period expired. I lost count of how many powerheads I installed months after the warranty expired at no cost (parts or labor) to the customer.

However, it's nice of you to step up to the plate to be the first in line for progator135 when that #1 piston starts peeling apart. :cool:
 
Joe, what happens to the oil once it goes through the carburetor and how long could a given droplet of oil remain inside the crankcase ??
 
Chris Carson has done extensive studying of the oiling systems.
Currently I am experiencing excessive oil consumption in a 2004 225HO DI.
I asked him what would be the probable cause and we discussed various things that could contribute.

He suggested I disconnect one of the oil pump output lines from the pump, and connect my own small line to catch and measure the oil per a given period of time.

HUH??? Disconnect the oil to a cylinder!!!!!!!!!!!
WTF Chris?

He replied in his testing he has disconnected oil lines to measure flow many times. He disconnects for quite a long time, minute or so, if I remember right.
And after he does this, he has disassembled engines, and always the cyl with no oil supply for a minute, has plenty of oil coating everything.
He is satisfied that at idle with no oil supply, the cyls will not run dry.

Now....you experts are gonna say....hey, the DI has a small bleed of oil directly into the incoming fuel line....and yes I know that. I am very sure it doesn't mix at 50 to 1 though. It is just enough to lube the injector pintles properly.

So, I guess the question is still open...

But anyone that has disassembled an engine will remember how oily it is....it cannot disappear immediately after the carb goes dry.
 
Once more these discussions prove that lubricatiobn inside a 2 stroke is not well understood.------Many folks just do not know the simple things on how oil actually behaves inside a 2 stroke !!!!
 
Is your vro hooked up if it is you are just filling up your carbs with oil. I have a similiar motor I just run brp 2+4 fuel conditioner and leave it alone always ready to go when i am and my boat can sit for storage over winter.
 
Ah... It is a mystery that coincides with the Spinx... like the Energizer Bunny... it goes on and on and on.......
 
Racerone how is it a ratio if the fuel has been disconnected. When you pull the fuel line on a working vro the oil side does not stop working it keeps pumping. So since the fuel has stopped pumping the oil side fills the line and carbs up. My motor is a 1986 70 hp evinrude with a working vro I have run it out of gas hard starting and smoky when you restart for that reason.
 
The oil pump side is only a wee piston and it does not pump a lot .It pumps only 2 % of what the gas side pumps.----------Hard to start you say ?-----Do some trouble shooting as I do not believe it is due to too much oil !!
 
No thank you racerone it starts and runs fine. i just put it in storage with the carbs full and brp 2+4 in it works every time. I can only give you the facts I cannot make you believe them.
 
Yes if no petrol in the tank yet oil in the vro tank and keep turning over it will fill the carb with oil if you keep trying to
start it.
When petrol is being pulled through its a sort of ratio, but not an exat ratio, that's why the VRO is total crap..
No exact ratio can be determined , even omc knew that, it states "variable" ratio.
But the is no definite ratio at any given rpm, even the OMC boffins did nit have any proven files on the gimmick.
On the oil side of the pump the only electrical sensor is for "NO" oil alarm !!! .. the "low " oil alarm sensor is in the oil tank.

When turning the engine over, the pulse line operates the pump diaphragm, the pump does not have a fuel sensor , just no oil
sensor s will keep on pumping oil through the line.
The oil side often lets to much oil through and causes hard starting and too much smoke .
Also more often don't let enough oil through its tiny pipes and causes piston failure.

Not many people take note of exactly how much oil they use compared to petrol, so they don't now if their vro Is
working properly or not.

some say about x amount they "think" !!!!,
yet everyone who use pre-mix knows exactly what their oil ratio is.

so yes the oil can fill the carbs right up, mine did exactly that before the oil stopped pumping enough oil.
 
Years ago I had an old 2 stroke lawnboy mower. It was already 10 years old when I retrieved it from someones garbage. cleaned the carb and it ran for another 20 years. The shutdown method was always to turn the fuel valve off and run it out of fuel at the governed speed of approximately 2500 RPM. It never seemed to be a problem...the mower was still running well when I gave it away. I now own a 1990's Merc 2+2( Yamaha design) 115 HP...it is designed to run on the top two cylinders below 1800 RPM. The bottom cylinders do not have traditional idle systems and therefore receive so little gas(and oil) at low RPM's that although the spark plugs fire, there is not enough fuel mixture to explode. Hence, the 2+2 designation. There are thousands of these motors still in use and I dont believe the reduced oil supplied to the bottom cylinders created any problems.
 
We could get blisters on our finger tips trying to teach.--------Or blisters on the tongue.---------Some folks are confident that they know how it all works.-------Had an individual call me for a flywheel for a 40 year old Mercury.---Was in a panic for it.-----------Then called and said his " mechanic " said it also needed a stator.----I said " time to look at this motor " before spending another penny.------------Looked at the motor and quickly determined that all the wiring was rotten.----Transom on the boat was rotten too.-----Individual had already bought a new trailer for this piece of junk too.-------Individual than said ---" thank you very much for top notch advice "-----Saved him a bunch of agravation and money too !!
 
OK one more time. I will use this as an example when they develop a leak in the fuel side VROs tend to smoke more. Because of the air it is pulling in the pump speeds up and pumps more oil because it thinks the motor is calling for it. If you pull the hood and listen to the pump most of the time you can hear the pump clicking from speeding up from sucking air because of the leak. Ok ya with me so far. Now when you pull the fuel line off it mimics the same problem the pump speeds up and pumps more oil and less gas because there is no gas to be had from disconnecting it. This happens because because it tricks the pump into thinking it is getting behind so it tries to catch up. Result the pump speeds up. This shows up usually as a clicking sound. This tricks the oil side into thinking it needs to pump more oil. More oil into a line with no fuel so the whole time you think you are running the carbs dry you are filling them with oil. By the way 2+2 mercurys are mercury built and designed not yamaha. Yamaha never designed a blind bore block for mercury products. At least according to my former 1996 125 2+2 merc. And trust me those are well oiled cyl on them they have scavenging lines on them. Did you really think mercury would warranty a motor that couldn't keep the cyls oiled.
 
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