1995 502 MAG EFI

After running antifreeze thru the cooling system, I pull the coil wire off and spray fogging fluid into the throttle body.
When I do that, I slide the throttle lever forward to open the blades and then spray fluid into the housing as I crank the starter to turn the engine over.

Question is , is the engine adding fuel to the fixture when of I do this

Just as it would under normal start conditions yes

well that sucks, the fuel is washing out the fluid.

So how do I fog and efi, pull the plugs??

With throttle in WOT position the ECM is placed in flood mode, which keeps the injectors from firing. Even if they were firing it would not be that much fuel

Another issue I would be more concerned with is fogging oil in the intake plenum. MPI motors should not be fogged because it coats the sensors. There is a tech bulletin out saying to mix up a gas and 2 cycle oil mix and run the motor on remote tank, which moves this stuff thru the fuel system

Thanx for the replies.
In previous years I would drain the metal spin on fuel filter and spray a few ounces of fogging fluid in it and crank the engine on that.
Each spring on the first day of boating the engine would stall after a short bit off running and take a very long time to restart.
I assumed that was due to my fogging method, so I decided to change that.
Sounds like I may just not fog it.

Might not be the best way, but I don't fog mine

not one marine OEM engine manu has ever recommended fogging a EFI / MPI thru the intake. One is all your doing is coating the intake track and the runners alot with fogging oil and 2 is it messes up the map sensor and in apps that have a TMAP it really messes up those. And also depending on if applicable and location the fogging oil is messing up the IAT sensor. Also not good for the IAC to be coating them with fogging oil. Next is if your app has a IAC muffler you are really hurting the IAC causing a restriction.


Volvo penta come out with the best way to lay up marine engines in 1996. Merc followed that same procedures in 2001. But with way too much 2 stroke oil in the mix for a jist.

If you are going fog an efi engine, mix some 2 cycle oil or Marvels' Mystery oil into the fuel inside the water sep fuel filter.
Then after fogging, replace the fuel filter with e new one filled with fuel and a little Stabil.

My only concern would be the oil plugging the filter. I would imagine the straight fuel in the Spring would pretty much clean it out though.