run float bowls empty?

[dingbat]

Re: run float bowls empty?

If one cylinder is run dry while another is making power there is significant risk of cylinder damage.

Lots of people have blown up outboards that they kept running after a cylinder lost fuel.

I have done a lot of stupid things, but that is not one of them.

I'm not talking about a lean condition from a carb problem. I'm talking about running your fuel tank dry.

 

[rodbolt]

Re: run float bowls empty?

woulde it just be to simple to drain the carbs? that is why most have drain plugs.
most carbs and all multi-cylinder yamaha carbs (US market) have a pilot fuel jet.
that jet is about 3/8th" or more from the bottom of the bowl, by design you simply CANNOT run the bowl dry.
climate,fuel and oil mix all have an effect on varnish formation. in this area its warm and humid enough that if you simply ran the motor till it quit and let it sit 4 months odds are high you will have the bowls off for cleaning.
on the above 40 yamaha oil is injected behind the carb into the intake area so if the crank is turning it is getting oil.
the above 40 also has a drain screw in each carb.
on the above 40 the drain screw is cross drilled and if not already plugged only requires it to be loosened a few turns for draining.
with our new E-10 fuel this spring otta be interesting.
nasty stuff when your dealing with fuel injection,high pressure pumps and 150 gallons at a time.

 

[pvanv]

Re: run float bowls empty?

Agree with rodbolt and TG, and others. It won't hurt to run these "dry", since the oil is injected after the carbs, but it also won't drain them all the way. The drains are very near the bottom, while the carb jet draws are higher. The bowls can't be fully drained by running. If storing for more than a month or so, best to drain everything -- lines and all -- as the Tohatsu factory does on fuel-injected 4-strokes before shipping to the dealers, especially with the junk E10 gas we have these days.

 

[coolguy147]

Re: run float bowls empty?

what the older outboards with 24:1 mixture say a mercury? well i nvr seen this thing evr run or do i know if my grandfather always ran it dry but. i have a 61 merc500 which is 24:1 mixture and two gas tanks with it right. so im sure at some time they were crusing along in the engines life and ooppps ran out of gas one moment gotta get the other tank u know? my grandfather was a great guy at all engines but dont know if u evr thought about the cylinder running without looob. and took the idea that it was a 24:1 mix. u think any damages major damage might have occured? most likely not. what u guys think? to get to the point. if u mix 24:1 would it hurt to run dry?

 

[Woodnaut]

Re: run float bowls empty?

Depending upon the particular carbuerator setup you have, you possibly could damage the engine. For example, I had an old 2 cyl Gale OB from the 50s that had a single carb. Running the engine dry, and then choking it right before it died (to get the last bit of gas out of the carbs) never damaged it.

However, years later, I owned a 150 HP V6 Merc which had 3 dual-carbs. As I recall, the "fuel enrichment" system was not the same on all three of the carbs. Therefore, choking the engine to get that last bit of gas out of the carbs wouldn't actually work all that well and probably would cause cylinder bore damage on at least two of the cylinders.

Bottom line is that draining the carbs gets the job done well and does not damage the engine. The "risk versus benefit" may not justify running it dry.

 

[rodbolt]

Re: run float bowls empty?

that old Gale from the 50's also had massive jetting, adjustable high and low speed needle, used roughly a 24/1 pre-mix and the 35HP version burned gas like it was 10 cents a gallon.
most modern outboards went to fixed jetting for the airfuel mix at idle,intermediate and high speed running.
doesnt take much varnish to lean out an already leaned out air/fuel mix.
most medern carbs the idle fuel jet is located 3/8ths of an inch or so above the main jetting and all fuel normally goes through the main to get to the idle jet.
makes the package smaller,lighter and more efficient.
most modern carbs are also of a back draft design to further lean out the mix at midrange throttle settings.
depending on your locations air temps and humidity levels coupled with your fuel blends for that geographical location some folks get away with almost anything and some get away with nothing.
my theory is if its not there and the bowl has been drained there is nothing to cause varnish nor gum buildup and all is well next season.
in my opinion running a fuel bowl dry at idle speeds and no load simply cant hurt an outboard, you also simply wont get all the fuel from the bowl.
the issue starts the next season when its run at a lean air/fuel ratio and takes out a piston.
watch the forums come spring and look at all the posts about it starts well,idles ok but when I give it gas it dies, the reason is universally gummed up main jet that allows enough fuel for no load idle but nothing more.
where did that gum/varnish come from ?
so if its worked for you in the past by all means keep doing it, just be aware our fuel blends,additive packages and fuel quality is changing rapidly and seasonally.
be aware that just because it used to work doesnt mean it will always work.

 

[artherm]

Re: run float bowls empty?

I have been boating fifty years. My dad always drained float bowls before trailering. He believed in it. I had trouble starting my 25hp rude a time or to at launch, one time would not start at all. Returned home, pulled carb and pretty much determined float was stuck shut. This actually happen year before, and never did figure it out. I use standard mixture, plus Seafoam. I think setting between using stuck needle/seat. I have since started running engine dry, this season, w/o any starting issues. Cleaned carb thoroughly with solvent. I found no dirt or residue internally to cause problem.

3 hp rude
6 hp rude
9.9 rude
25 rude