engine fogging

[KJM]

well its that time of year and i'm wondering about fogging the engine. i usually remove the plugs and spray oil into the cylinders but i've heard that you can just spray the oil into the air intake while the engine is running? whats best and how much oil would you spray into the intake? until the engine stalls maybe?

 

[Scott Danforth]

the purpose of fogging oil is to coat the interior of the combustion chambers so that an open cylinder (one with a valve open due to the cam position) doesnt rust.

most V6's and V8's wont stall, unless you dump enough to hydro-lock them.

simply spray fogging oil in intake (carb, throttle body, etc) smoke up your area, and key off

you could also simply add 2-cycle oil to a small tank and run the motor on the small tank.

Me personally, I dont fog, never have, never will. a 2-stroke outboard has enough oil in the fuel to already be "fogged", and for any I/O, simply change lubes, drain water and stow = winterized.

 

[KJM]

thanks, i'll probably go the intake route this year, sounds easier. i know it probably isn't necessary but i rest a little easier knowing there is a nice coating of oil in the engine during the winter months.

 

[Lou C]

It depends on the storage conditions where you store your boat. If is a warm climate with little condensation on metal surfaces, or a dry climate it is not so necessary. If its a damp cool climate like Long Island in the fall, winter and spring, I feel for sure it is worth it. When I open up the storage cover to charge the batteries etc over the winter, if its been damp out the engine is covered in condensation. Happens in side too. So I fog and back fill with good marine AF to keep out air.

 

[KJM]

yeah, its definitely damp and cool here most of the year! So you think antifreeze makes a big difference for corrosion prevention over just draining the engine? I guess corrosion inhibitors are better then air. Didn't know there was even a such thing as marine AF, I've just been using regular car AF and was considering just draining the engine and leaving it at that this year.

 

[stonyloam]

Your engine was filled with WATER all summer, and is already coated with a layer of rust, so having it full of AIR during the winter months will do no harm whatsoever.

 

[Lou C]

Ahh well try this.
​One year just drain.
Next year use Marine (Not car) antifreeze Marine=propylene glycol, is not toxic, car=ethelyene glycol, very toxic

​watch what happens when you start up. when you use AF there is no rust in the exhaust water, when you don't there is.

 

[KJM]

Really when you think about it, the inside of the engine isn't going to dry out over the winter when you drain it, so wet iron and air = rust. If you can stop the rust with AF for 1/2 the year i guess thats better then rusting all year long.

 

[stonyloam]

OK for all of you guys that are concerned about rust. 2 gallons of air contains about 1.5 grams of oxygen. So if you consume ALL (not likely) of the O2 and convert to Fe2O3 (rust) it will add up to about 3 grams. If you put the plugs back in, no more air will get in. Since you have about 130,000 grams of iron in your engine I would not lose any sleep over it .

 

[KJM]

Just for arguments sake, i would guess that air can get in thru the water intake and past the impeller. Having said that, i took the easy way out and just drained mine and left the plugs out.

 

[Lou C]

Its better to put the plugs back in, if you are in a humid climate because even just doing that, it reduces rust in the threads. A bit of Merc perfect seal or OMC gasket sealer works wonders for keeping threads in cast iron from rusting.