Carberator build up from old gas

[CWCW]

I had an older gentleman who has been a long time fisherman tell me that he has an old evinrude 40hp 2-stroke motor on his boat and he will undo the fuel line from the motor everytime he pulls his boat on the trailer to load to go home and he runs the motor in idle until all of the remaining gas is burned inside the motor. (The motor is still in the water during this time to keep the motor cool of course) He claims that it will keep any gas left in the engine from ageing and that he has never had to clean out or maintance his carberator because of him doing this. Is this a bad idea?

 

[Laddies]

Re: Carberator build up from old gas

If you don't know how long the unit is going to sit it's a good idea to run the fuel out to prevent the varnish build up in the fuel system.

 

[Silvertip]

Re: Carberator build up from old gas

Two schools of thought on this topic and it's been beat to death. Run a fuel treatment like Stabil or SeaFoam and forget about running it dry. However on a portable motor that makes sense as you don't need fuel dribbling all over when the engine is layed over. On a trailer boat however, most engines have multiple carbs and oil injection. All carbs will not run out of fuel at the same time and therefore one or more carbs will still have some fuel in it. Now the float is dropped because the float bowls are not full. If an oil injection check valve leaks a little, you could end up with carbs full of oil. Not the case on an OMC since the oil tank is remote. Lastly, since the engine is running lean just before it quits, it is also lean on oil. Is that worth taking a chance on when a shot of Stabil in each tank of fuel is all that's needed.

 

[Lone Duck]

Re: Carberator build up from old gas

I agree with silvertip. I am a retired small engine mech. Mostly lawn mowers and chain saws. a few welders etc. I have found that if you put in a fuel stabilizer and run it for a while and make sure your tanks are full. You have fewer problems. Also I discovered that when you do run into a carb. that is full of that brown and green gunk . wash it out with meythlehydrate . It is the best thing that I have found. Stick it in a can full for an hour then blow it out with WD40 and air.

 

[Laddies]

Re: Carberator build up from old gas

Just two points for the stabil side If you read the instructions on a can of stabilizer it tell you to add so many ounces of product for each gal of fuel per month, how do you know how long a unit is going to set! If not used properly these products cause there on type of crud. Then we have the wonder juice that cures all problems according to some if you read the product info on it, it is about 90% alcohol, who would put alcohol and fine oil in fuel and expect it to stabilize it, don't we have a enough problems with alcohol in fuel without adding more?
The short winded answer for running a engine dry is most people that do it have the common sense to use the choke while doing it and that causes the engine to be loaded up on oil not be lean.

 

[MercFan]

Re: Carberator build up from old gas

I've never bothered with either running my carbs dry or adding stabiliser.
To me the fuel will evaporate from the float bowls and since I don't have oil injection, my carbs will be left with a layer of 2 stroke oil on the inside. So I don't see any problems with varnish.

The fuel might very well go stale, but it's not like it's an aeroplane that puts my life at risk if the engine dies. I try to run my portable tank low before hand though. Say below 1/4. Then I just add fresh premix in the summer. I disconnect the fuel coupling from the engine, actuate the non return on the tank side, pump the primer a bit to get some fresh fuel there, connect and startup. It smokes a bit in the beginning from all the oil in the carbs and cylinders, but after that, no problems. I could possibly be losing a couple of horses due to the stale fuel mix, but hey, I'm not trying qualify for F1 in my boat.

 

[Texasmark]

Re: Carberator build up from old gas

I use Berryman's Chem Tool (red-white-blue can) aerosol, or pint can available at any auto parts store. Made for just that.

On stabilizers, I understand that ethanol does not respond. Dunno personally.

On running dry or not, did both and never had a problem either way.

Mark

 

[j_martin]

Re: Carberator build up from old gas

On a 4 cycle engine, or 2 cycle with pre-mix, the best bet is to run the fuel out, leaving the floats hanging with the needle valves open. On a VRO engine, it could cause a problem with excess oil in one or more carbs.

My carb'd V6 stays hooked and is just shut off between uses. I unhook it and drain the carbs for long term storage.

All my small engines are run dry every time they stay off overnight or longer. They seem to have very little carb troubles compared to when they were left with gas in them.

hope it helps
John

 

[Cornell]

Re: Carberator build up from old gas

I bought my 1973 Merc 7.5 hp new. I always ran the carb dry while at boat dock, waiting for triler pick up. Carb has been great for years. However, I feel that needle and seats might be dirty now after 34 years. Having start up problems. I try to keep my fuel tank indoors (garage) and on wood or cardboard to lesson condensation. Tank looks clean all this time. Cornell

 

[Texasmark]

Re: Carberator build up from old gas

Added note here. I would not run anything dry that wasn't pre-mix. I think I started leaving it in when I got my tower in '89. Don't remember why..............wait, it just hit me; it wasn't pre mix; had a separate oil tank so it had to be the first attempt at oil injection.....kinda a kluge attempt at adding new technology to an old engine mechanical design......but it worked.

To test the oil alarm, unstrap the oil tank from the boat and turn it upside down.

Mark

 

[pman7]

Re: Carberator build up from old gas

I use Berryman's Chem Tool (red-white-blue can) aerosol, or pint can available at any auto parts store. Mark

Unless something odd happens that causes me to forget, I always disconnect my gas line and run it untill she stops. Done so with all three motors I've had. The newest is an 82 and all 3 were premix. Has worked well for me.

Texasmark, glad you brought up Berryman's. I've mentioned it before and I used to use it. People here have talked me into using Seafoam. For the life of me I can't see much difference (except cost) in the way they perform. Both seem to keep my motors clean and idleling smooth.

Maybe Berryman's is a bit stronger in the aspect of dissoving gunk(just a guess as I don't have evidence to back up my statement other than seeing how well it cleans up varnish and gunk) but Berryman's doesn't seem to get much mention on this board.

TM, what's your opinion on a comparison of the two?

ps: hope this isn't considered a thread hijack because it still is on the subject of carb buildup.

 

[j_martin]

Re: Carberator build up from old gas

I bought my 1973 Merc 7.5 hp new. I always ran the carb dry while at boat dock, waiting for triler pick up. Carb has been great for years. However, I feel that needle and seats might be dirty now after 34 years. Having start up problems. I try to keep my fuel tank indoors (garage) and on wood or cardboard to lesson condensation. Tank looks clean all this time. Cornell

I think you could probably justify a carb kit by now. I would suspect that the original float is foam, and has been done in by alcohol in the fuel. You could have gotten another 30 years out of it by using "nonoxygenated" fuel.
The new hard plastic floats can take the alcohol.

34 years is pretty good service life on a needle and seat, also.

hope it helps
John

 

[Merc25XD]

Re: Carberator build up from old gas

Talk about longevity...I still use the 1964 6hp Mercury that my Dad bought new. Paid $165....The ONLY thing that I have done to that motor is to have the impeller changed about 5 years ago. NOTHING else. Never ran the fuel out of the carbs. This motor still runs just great. Aren't Merc's great...

 

[Cornell]

Re: Carberator build up from old gas

For Info. My '73 outboard "Owners manual" says to drain the fuel out by disconnecting the fuel line and running while still in the water after each use.

 

[Texasmark]

Re: Carberator build up from old gas

pman

I use Berryman's for the major dissolving jobs, be it carb or grease on an engine (any engine) I am working on....like if I'm doing a carb kit, or installing a gasket (anywhere) and want to degrease the surface.

If adjacent painted surfaces are involved, and it's grease, not gas/varnish I use spray brake cleaner....gets the grease, not paint like Berryman's does. Also great for pre repainting where you want a greaseless surface for the new paint.

I use the Sea Foam in the fuel tank with every fill up.

Mark

 

[Marlinman10]

Re: Carberator build up from old gas

I have a 1972 Evinrude 6hp that my Dad and I bought new when I was a kid. I still have that motor today. It has many many hours on it and it runs perfect. I always ran the fuel out of it when done. I would pull the plugs and squirt marvel mystery oil in the cylinders when the summer was over. This thing has sat for years at a time and still starts right up and runs great.It's been tuned a few times and the water pumped has been replaced a few times too. The carb has never been touched.