Answer straight from PCM regarding fogging of engines...

[IDBoating]

Mercuay marine has a new fogging methiod for all carb, EFI, MPI motors

they mix
2stroke oil
stabilizer

Mercury gave me that recipe for what they call "witch's brew" many years ago, but I believed it was only for 2-stroke engines (whose injectors expect to have oil passing through them). Are you saying this is cleared for use in 4-strokes where the injectors are designed to pass only gasoline?

[raythompson]

Fogging 4 Stroke Engines

Mercury gave me that recipe for what they call "witch's brew" many years ago, but I believed it was only for 2-stroke engines (whose injectors expect to have oil passing through them). Are you saying this is cleared for use in 4-strokes where the injectors are designed to pass only gasoline?

I believe when fogging 4 stroke engines the mixture is sprayed, or squirted, into the manifold for ingestion in the cylinders. The mixture never passes through the injectors so the injectors will still pass only gasoline.

[TRD]

My boat sits for about 4-5months through the winter months. It is cover and out of the weather. I do fog my engine w/ fog oil every year using the small opening under the spark arrestor. With that said I also run marine stabil (double recommended) in the gas and when I take the boat out the 1st time next year I use 1 can of seafoam. After I run most of that tank of gas out I change my water/fuel seperator.

I haven't had any issues yet, are you guys saying I will it just a matter of time? At this point it would be just as easy to pull the spark plugs and put the oil in the cylinders, turn engine over by hand and this way not bother w/ the fog oil at all? The injector would be out of the loop at this point correct.

[IDBoating]

I believe when fogging 4 stroke engines the mixture is sprayed, or squirted, into the manifold for ingestion in the cylinders. The mixture never passes through the injectors so the injectors will still pass only gasoline.

Got it. That's how PCM instructs you to inject fogging oil into their EFI engines too - through the spark plug hole.

On the Mercury 2-strokes, you mix up the "witch's brew" in a separate fuel tank and run the engine on it for a while, so it gets everywhere in the fuel system including the injectors.

[IDBoating]

At this point it would be just as easy to pull the spark plugs and put the oil in the cylinders, turn engine over by hand and this way not bother w/ the fog oil at all?

For my EX343 engine, PCM recommends fogging oil be squirted into the cylinders via the spark plug holes - not regular oil. Then the crankshaft is turned manually a few times to circulate the fogging oil.

[JUST-IN-TIME]

no mercurys new mix is porued into the fuel filter then you run the motor for 15 mins

this is for all 4 stroke motors

2 stroke motors get like a 25/1 mix o oil to gas

this mix is like 1000/1 mix, so you do not clog the injectors up with oil

[IDBoating]

no mercurys new mix is porued into the fuel filter then you run the motor for 15 mins... this is for all 4 stroke motors

That still runs it through the fuel system, so the difference is in the mixture and not the method of application.

Thanks!

[JUST-IN-TIME]

yes mixture

fogging oil is a thick sticking oil

if you spray it into any efi motor, the map, baro might get clogged up

as for an o2 sensor after the cats and before the oil will burn off only if you put through the intake

if you put it in the cylinders and start it up, thats oil is going to hurt the o2 sensor until you burn it off

[IDBoating]

fogging oil is a thick sticking oil... if you spray it into any efi motor, the map, baro might get clogged up... as for an o2 sensor after the cats and before the oil will burn off only if you put through the intake... if you put it in the cylinders and start it up, thats oil is going to hurt the o2 sensor until you burn it off

That's the problem - different advice from different sources. I got completely opposite advice, "Do use fogging oil" and "Do not use fogging oil", from PCM in the same phone call!

The PCM guy who said to use fogging oil said "follow the instructions in the manual", which explicitly says to use fogging oil on their EFI engines. One local PCM dealer does fog EFI engines, while the other does not. Some on this website, including now you {grin}, say not to do it while others encourage it.

It's exceedingly hard for us out here to know the right thing to do. For this winterization, I got more votes for fogging oil than against (including more PCM votes for than against). So I did everything else to my engine and then shot fogging oil into the spark plug holes and manually rotated the crankshaft a couple of turns (which was exceedingly hard to turn, even with the plugs out - had to use a socket wrench on the crankshaft pulley). Sounds like my O2 sensor may be a little unhappy at first next Spring.

What do YOU recommend - just leaving the cylinders bare? I can do that but it doesn't sound too safe.

[JUST-IN-TIME]

a 4 stroke motor alsways have oil in the cylinders

a 2 stroke does not, it gets it oil from fuel

we run the cocktail mix from mercury on all EFI motors

never had a problem

if you do fogg you need to keep spraying it until the motor dies and keep spraying 10 seconds after that

[IDBoating]

a 4 stroke motor alsways have oil in the cylinders

Not above the rings!

if you do fogg you need to keep spraying it until the motor dies

Can't do that if it's being introduced via the spark plug holes.

[JUST-IN-TIME]

above the rings is very very minimal space, its like nothing, the piton always comes to the top of the cylinder, so the cylinder is fine, its the combustion chamber is what your worried about, which is not a big deal

but moisture on the cylinder walls is bad, rust will form in under an hr

your taking this way too far, and reading way too much

i would listen to mercury more than any other company, they been around longer than the rest and the only ones that build race motors

[IDBoating]

above the rings is very very minimal space, its like nothing, the piton always comes to the top of the cylinder

Except that when the pistons come down, the rings scrape the cylinder walls - ideally completely (or the engine would consume oil). No matter where the crankshaft is when the engine stops, some of the pistons are going to be "down" some distance, which means exposed cylinder walls with no oil on them. That was the point I was trying to make... some number of cylinders will be left without oil by the very design of a 4-stroke engine.

[JUST-IN-TIME]

like i said

your taking it way way too far, its cool thou

2 things ruin your motor quicker then anything

warming it up while not under a load

and revving motor over 1500 rpm with it out of water in neutral

[IDBoating]

your taking it way way too far, its cool thou

Hey, I'm just a poor boater out here. I can't afford expensive repairs so I need to take good care of what I've got!

2 things ruin your motor quicker then anything

warming it up while not under a load

Really? Why is that bad? I warm up while puttering around the lake anyway, so no harm here, but what is the disadvantage of being out of gear if the RPM's are still at idle? Or did you mean to say that it's bad to warm it up entirely at idle RPM's?

and revving motor over 1500 rpm with it out of water in neutral

Again, why? I don't do it, but... as long as the engine has adequate cooling water and you're not turning the transmission/v-drive/propshaft, why does the engine care if the hull is in water or not?

Trying to get smarter here, thanks for being patient with me.