Logo
FULL SITE MENU

melting a piston do to lean carb .

Status
Not open for further replies.
4

48tony

Regular Contributor
just wondering. ihave heard do to running the carb air fuel mix on the lean side it can burn out pistons. my plugs are the light brown color .they were dark and burnt looking before i leaned out the carb.the low speed needle valve was turned in 5\8 of a turn then i slowly adj till i got hi rpm. it seems to run real well no matter how much or little i adjust in or out.with the needle a1\4 turn out seems to be the spot she purrrs. just thinking it may be to lean but plugs show tan not white. any clues.
 
Your carburetors are fixed high speed jets and adjustable low speed jets.-----------------Low speed jets only affect idle performance.-----------------You will never burn a piston with low speed set too lean.------------------------------Most people simply are not aware of running the carburetors empty when done boating and this leads to plugged high speed jets and that is trouble.----------------So if you are worried clean those carburetors ( high speed jets ) and always , always run the fuel out when you pull the boat out of the water!!!--------------Some will argue that it is not the proper thing to do but that is nonsense.
 
Im reading this post and not quite getting your point. You are trying to say that running your carbs empty will be a good thing ,since left over gas will clog high speed jets, correct?
 
(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
 
that makes good sense.no fuel no oil.so dont run carb dry when taking the boat out of the water.ill keep the jets clean usin sea foam. easy and safe.
 
Absolute nonsense !!---------Oil coats the parts in a 2 stroke in order to lubricate them , it does not work any other way.----So when one carburetor runs out of fuel the oil does not instantly disappear from the CAST IRON cylinder wall where there is but 0.002" clearance ( per side ) with the piston. The oil can not instanly disappear from inside the roller and ball bearings.-------------------------When that one carburetor runs out of fuel there is nothing but air going thru and nothing washes the oil off the parts.-------------------RUN THEM OUT OF FUEL when you take the boat out of the water.------------Repairing outboards since 1968
 
During season I used to do it 'simple'.
Whenever stopping for the day, just pulled the choke or pushed the key to stop.
Never had problems re-starting, never had problems with clogged carbs.
If a VRO engine, remember that when pumping the bulb and re-filling the carbs it gets just fuel and no oil!
 
Well now, all of you fellows who would like to follow racerone's theory and go against OMC's recommendations, I strongly suggest that you have his location handy and on file. Run your multicarbed engines out of fuel every time you're done with them for the day.... and when you suddenly find that, for some strange unknown reason (cough), piston sidewall scoring appears, I' m sure he'll be glad to help you out with your problem.

And frankly fellow, I take a very dim view of having anyone reflect upon my marine line knowledge as "absolute nonsense"! Having been in the business since 1960 and strongly associated with OMC for many of those years, I have a pretty good slant on what is proper and recommended, and what is not.
 
Last edited by a moderator:
I can not imagine some one saying that oil instantly disappears from CASt IRON cylinders and from the bearings.
 
Oil does not INSTANTLY disappear, no one even suggested that, but an oil film breaks down over time.
However the oil film has another, often forgotten, function except the lubricating one.
The film is what transfer the heat from bearings to rods, from piston skirts to cylinder walls. Remove or reduce the film and you will reduce the heat transfer and create 'hot-spots' where you do not want them!
In a 4-stroke, about 30% of component cooling is done by the oil, not too much difference in a 2-stroke.
 
If running out of fuel was " bad " for a big multi carburetor 2 stroke you would think that the OWNERS MANUALS would have a full page warning, but they don't------------------------You would think that the 6 gallon portable tanks would have a low fuel warning or shut down system to prevent running out of fuel , but they don't and never have.------------How many big motors have run tanks empty time after time with no ill affects at full throttle / load.
 
Status
Not open for further replies.
Back
Top