Running Gas Out of Carbs

mulv80 · Jun 2, 2004

I just purchased a 2004 Yamaha 25hp 2 stroke. I'm trying to do everything right. This motor has two carbs one for each cylinder. The mechanic at the dealer I bought the motor from said to run the gas out of the carbs. I only run the motor on weekends so I dont want the carbs to gum up from lack of use. However my question is, Will I be running one cylinder lean and damage my motor since both carbs are unlikely to run out of fuel at the same time?

Ray Neudecker · Jun 2, 2004

Re: Running Gas Out of Carbs

No reason for concern. They also have a drain screw on the bottom of the bowl, but the easier and traditional way is to disconnect the fuel line and let the motor run until it quits.

JB · Jun 2, 2004

Re: Running Gas Out of Carbs

Hi, Mulv80. I strongly disagree with the wrench at the dealership and mildly disagree with Ray. Running a single carb premix engine dry is probably harmless. Running a multicarb premix engine dry is an invitation to damage, for the very reason you are concerned about. Running any oil injected engine dry is guaranteed to gum up carbs unless the oil is injected directly into the crankcase, then it only fouls plugs and generates a smoke screen on restart. Take the extra time to drain the carbs when you put her up for a while. Good luck.

rodbolt · Jun 2, 2004

Re: Running Gas Out of Carbs

gotta go with JB again. you cannot run the carbs dry. there will always be a bit left in the bowls. normally its that last bit that clogs the idle jets. drain them and dont sweat it. good luck and keep posting

Merc805 · Jun 2, 2004

Re: Running Gas Out of Carbs

My 2 stroke motor has had the fuel run out since it was made in 1980. No problems so far.. but hey... it's only 24 years old.

JB · Jun 2, 2004

Re: Running Gas Out of Carbs

What category is your engine, Merc? I also did that for years on several engines, but my float levels were always precisely matched. Even so, I had to clean the carbs more often than after I started draining the bowls instead. I do run my '48 Sea King out, and it is only 56, but it is a single carb premix engine. I stick to my recommendation.

Ray Neudecker · Jun 2, 2004

Re: Running Gas Out of Carbs

Yamaha does inject the oil behind the carbs. I like the idea of the engine going up with the extra oil in it. I also agree the surer way to keeping the carbs clean is to drain them. You do not burn off all of the fuel in the carb and there will be shellac formed over the years. No matter which method you use you are still likely to have to service the carbs at some time if you keep the motor long enough. If you are not prepared to do the job of draining them, then run the fuel out through the motor.

Merc805 · Jun 2, 2004

Re: Running Gas Out of Carbs

JB I agree with you on the draining.. as that is the ultimate method. On my 1979 50hp Mercury, you can't access the bottom carb plug as it's right down near the shift shaft lever and you can't even see it. I remove the fuel line and run until the motor starts to pick up speed and then shut it off.. per 12footer. I also religiously start and run it monthly when not being used. I also ALWAYS use fresh fuel (no more than 4 weeks old) and staibiliser. The previous owner told me he has always ran the motor until it stalled. I made the mistake of leaving the fuel in the carb of my other small single carb OB once and the fuel evaporated leaving more oil. It took me all morning to get it started, and had to remove and clean the plugs about 6 times before it would run right.

mulv80 · Jun 3, 2004

Re: Running Gas Out of Carbs

JB How long can I allow the motor to sit before worrying about the carbs gumming up? I use the motor every weekend in the Summer but occasionaly may miss a weekend. Can the motor sit with fuel in the carbs for two weeks without concern? I will definitely learn how to drain the carbs before storing for the winter. Thanks for all your help fellas

JB · Jun 3, 2004

Re: Running Gas Out of Carbs

Two weeks shouldn't be a problem, Mulv80, unless it is stored in strong sun. Then I would drain them. Good luck.

LubeDude · Jun 3, 2004

Re: Running Gas Out of Carbs

Wow JB, I usually hold your replys with the highest reguards, but two weeks?? Ive never drained a carb in my life and never had any issues and do not use a fuel stablizer. I do however pump my bulb every once in awhile if Im not using the boat for a while. Just lucky I guess.

Merc805 · Jun 3, 2004

Re: Running Gas Out of Carbs

That is most likely why you don't have a problem. You are keeping the gas dissolved and mixed, thus eliminating drying out.

JB · Jun 3, 2004

Re: Running Gas Out of Carbs

I suspect that "strong sun" has different meanings in Texas and Orygun, LD.

In August under-hood temps can exceed 150*F, here. That will boil gasoline.

andrewkafp · Jun 3, 2004

Re: Running Gas Out of Carbs

JB How would I go about draining on my 1980 4 cyl 2 stroke Merc ? The bottom carb is not really accessable ? Ref here..

JB · Jun 3, 2004

Re: Running Gas Out of Carbs

There are some engines that prevent it, Unicorn. It looks like yours is one.

andrewkafp · Jun 3, 2004

Re: Running Gas Out of Carbs

Dohhh....

S'pose I could drill a big hole in the lower cowling...and have a removable rubber plug. A bit of good 'ol customizing

Running Gas Out of Carbs

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