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Do Four Stroke (yamaha F115) engines need to be decarbed?
If so, how much and how often.
I have twin 250 Yamahas that are carbeurated and I keep Ring Free in the gas tank all the time as well as the DeCarb procedure every 30-60 hours.
I am getting another boat with a Yamaha 115 four stroke. No experience with a four stoke. What is the procedure for decarbing or do these engines need decarbing.
Also, even if they do not need heavy de-carbing, will it hurt to run Ring Free in them occasionally?
If you have a good mechanic that you know and trust, ask him about using Ring Free in the F115. I know it's recommended for my oil-injected 90, but not sure about the F115.
I may be missing the point, but decarb has to do with two stroke engines. In makes no difference if their EFI or carbs. The question is do four strokes require decarb. I don't think so...no oil in gas! cool: [img]/infopop/emoticons/icon_wink.gif[/img]
[This message was edited by Mumblerone on 09-09-02 at 09:56 PM.]
[This message was edited by Mumblerone on 09-09-02 at 09:59 PM.]
I would think you would have to decarb the cylinders for carbon buildup. I would also consider doing it to keep your induction system clean. I'm no expert, but if it was my motor I would do it every 100 hrs.
I have torn down way to many four stoke motors that have had carbon buildup. Also keep your oil clean it will also reduce it.
As with your car engine, you should be able to use any of the various gas treatments (STP, etc.) to reduce carbon build-up (if that's even a valid concern for a 4-stroke outboard). I certainly see no reason to use a 2-cycle decarb solution in a 4-stroke.
Here is what I got from Boatsetup.com
Thanks every one for their help.
We (our dealership) have not experienced any carbon build-up on the F115's. With it being fuel injected you get a lot better burn of the fuel verses the carbed models. If you are running Ring Free I would continue to do so.........it will only help.
Since we are talking 4 strokes why use a additive that was developed for 2 strokes. If you burn Chevron gas, which has techron in it you should be able to take care of fuel issues such as keeping the injectors and valves clean. And with the use of techron you should also keep carbon buildup to a minimum. IMO the use of techron and keeping the oil changed at frequent intervals should keep your 4 stroke happy. What about PRI-G it should keep carbon at bay and stabilize the gas?
Sorry about my lame humor [img]/infopop/emoticons/icon_biggrin.gif[/img]
However, being fuel-injected, I would think that the need to decarb would be greatly reduced, if not totally eliminated via the use of Ring Free. I haven't asked my mechanic about this, though.
Allow me to ask you this, do you spray something down the fuel injection system of your car or truck every thousand miles in order to decarbonize it?
Do you add a non-ring scuff additive to your automotive fuel? What if they named it something like, "No plug FI treatment". You'd have to add something called "No Plug", wouldn't you?
Point is, you need to decarbonize a four stroke outboard about as often as you need to decarbonize a four stroke automobile engine: never. As far as that goes, many two strokes run very happily for thousands of hours without a decarbonization treatment. I have chainsaws that have many tens of hundreds of hours, and I've never cracked a plug loose! Of course, I didn't run Ring Free in them either, so maybe that's what has saved them!
Will your four-stroke outboard suck down Ring-Free and incinerate it in the combustion chamber? Absolutely! Will your Yamaha engine dealer recommend if for your four-stroke? I'd fall over dead if he didn't! He wants that cash, just like the Yamalube thang.
P.S., don't put just any high quality motor oil in the crankcase of that Yamaha Four stroker, sure, the warranty allows the use of "other" SAE motor oils, but if you don't use the Yamaha motor oil, that thing is going to grenade about two months after the warranty expires.
So remember, pay them now, and pay them later (no evidence exists that not using Yamaha lubrication products will cause an engine failure any sooner or later than if you used them. As a matter of fact, there are people on this board who've had power head failures and use Yamalube religiously. Well, if that's true, than what is the freaking point?)
As gasoline has changed, the amount of additives such as aromatics and oxygenates has increased. These additives are important for the engines in PASSENGER CARS, but they can have detrimental effects in marine engines, because of increased deposits in the combustion chamber. When enough deposits collect, piston rings begin sticking. Performance drops and engine wear increases dramatically.
While many additives available may reduce deposits, Yamaha recommends the use of Ring Free Fuel Additive. Ring Free has repeatedly proven its ability to clean combustion deposits from inside the engine, notably the critical piston-ring-land area, and fuel system components.
This is all taken from my F115 Yamaha Manual.
On a side- do you know that most gas is the same base product? In other words, most companies fill up the tanks from the same source and then add their additives, making it their own formula.
Best bet is to use the same brand of gas for a few hundred hours and then switch to another brand for a few hundred hours.
IMHO, Ring Free is not required on any 4 stroke engine. The carbon build associated with 2 stroke engines comes from the oil mixed in with the gas.
Any good quality gasoline has "cleaners" added. Higher octance is not a bad idea, especially if you a doing a lot of WOT with heavey loads (Skiing for example).
Mobil 1 is certainly an excellent oil. Its biggest benefit is viscosity stability over a wide operating temperatures. Outboards typically are not used at less than 32F and with water cooling (even with a thermostat) should never exceed 200F. I don't believe the substantial cost increase of any full synthetic will pay back compared to a good quality (SJ or higher) natural base oil.
As gasoline has changed, the amount of additives such as aromatics and oxygenates has increased. These additives are important for the engines in PASSENGER CARS, but they can have detrimental effects in marine engines, because of increased deposits in the combustion chamber. When enough deposits collect, piston rings begin sticking. Performance drops and engine wear increases dramatically. Posted by Firefly from his F115 manual.
Man, this statement in the owner's manual is truly suprising. Considering the additives most gasoline mixers use are detergents to cut down on build-ups, this sounds like a marketing ploy.
Why is a marine four-stroke engine so much different than an automotive four-stroke engine? Answer: it aint! It has pistons/valves/rings/lands/wrist pins/camshafts/crankshaft/lifters etc. etc.
Why would a "marine" four-stroke get piston scuff? It is a bunch of bunk. Piston or cylinder scuff happenend on two strokes that didn't get good lubrication because of poor quality oil or delivery.
Yamaha stating that their four-stroke needs Ring Free is like stating that their internal oiling and lubrication system sucks so bad that you have to add stuff to the fuel to ensure you don't dynamite your engine.
There are no significant internal differences between 4 stroke outboards and automotive engines, but big differences in their usage. You don't idle your car much, and most people drive their cars every day.
I don't own a 4 stroke OB, but if I did I'd decarb it once a year. I can't see it doing any harm and might save repair bills down the road.
I do have an old International Harvester Scout 4WD vehicle that I decarb every now and then because it only gets driven a few hours a year. It makes a huge difference in its performance. Much cheaper than an engine rebuild.
I'm not trying to be contentious, but the reason cited for using an additive to keep ring scuff down on the F115 four stroke was additives organic to pump gasoline.
If you follow that line of logic, you should never have to decarb your Scout, because of the scant hours of use it sees and the wee amount of pump gas additives are insufficient to "poison" it.
Now on a practical level I suppose it makes sense to decarb your old Scout, but probably more as a carburator de-varnish job, because old gas does evaporate and leave behind deposits.
Try this, before you put up your Scout for an extended time, starve the engine of fuel and then shut off the ignition. Then you don't have fuel evaporating and varnishing the jets and bowls of your carburator. Cover intake and holes to avoid mud dobbers setting up shop in the intake and heads.
Otherwise, it stands to reason that your slightly used engine shouldn't produce more carbon, it should produce less, because it is run so infrequently and benefits from added detergents and decarbonizers in modern gasoline.
This would be especially true if you didn't just idle around in your Scout when you did run it, but actually drove it at highway speeds now and then.
Four Stroke.. to Decarb or not to Decarb
