Fogging a fuel injected engine 350 Mag MPI
 

I read about people fogging an engine for the winter by slowly pouring down down the carb, but why cant a FI engine be fogged the same way? The engine I want to fog is a 350 MPI MAG.

Fogging is not recommended for Fuel Injected engines. You can actually cause more problems than you'll prevent by doing it. We only fog older carburated I/O's and outboards.

Is it because oil can accumulate in the intake manifold?

Fixx
 

Fogging prevents rust build up on your valves and seats..per merc manual all you have to do is remove the fuel filter and dump out a few ounces of fuel and replace the fuel with two stroke oil..this supposedly lubes the fuel injectors,valves and seats.. i do both,i run the boats i work on in a antifreeze bath good for -*50 below and while doing so i fog the engines weather its efi or its a carb..

Thats what i read also...

from 1995 to 2001 350 mag mpi,from 2001 til now 496 HO always fog with mercury spray can in the throttle body never got a problem.

Merc has a process explained in the manual where you mix the 2 stroke and stabilizer in a small fuel tank then hook it direct to the water seperating fuel filter and fog it that way. They say to run on the mix for 5 minutes @ 1300 rpm.

I always fogged the carb 500's, but since the 525 EFI's and the marina guys saying they just stabilize the fuel and run long enough to get it thru on the EFI motors, I've come up with a different deal. For the past 3 seasons I have added the fuel stabilizer, then added Lucas fuel additive, take one last run and shut it down and load it the trailer. Run the anti-freeze thru later and it's done. Works for me, fires right up in the spring and runs like a champ.

I assume the 2 stroke in the filter would achieve the same result as the Merc method. I just wonder how long you would need to run it to get the oil thru.


Actually a question here, how long would you need to run it to get the 2 stroke thru if you did the filter method?

At our shop we fog all injected motors and never ounce had any issues at all.

I just winterized my new motors(efi whipples) that Eddie Young built. I added Marine Stabil to my fuel, fired up the engines on water so that I could change the oil. Drained the block. Removed the fuel filters and added 5 oz. of Marvel Mystery Oil. I connected my antifreeze mixture. Fired the boat back up. It started to smoke just as I ran out of 5 gallons of antifreeze. Perfect. Probably 30-45 seconds.

OK, I'm going to correct myself and admit that there is a way to fog a FI engine - and several of you have noted it. I'm not in a salt water environment where fogging to prevent corrosion is a big issue, so going through the pain of opening a fuel line to introduce the fuel / oil mixture is something we've decided not to do. BTW, how many times can you break open a fuel line and not have it leak. Hmmmm. Anybody smell (literally) a liability issue for a marina here?

On the other hand, can anybody name the upstream sensor that doesn't like dirt / crud / oil getting coated on it - and is critical to your engine's proper operation? With carburated engines, you just introduce fogging oil right through the carb throat(s) for a bit and you're done. Do that through a FI motor and guess what gets crudded up over time? Food for through.

Just a hint on the Marvel Mystery oil. We did two boats a couple of years ago with the MMO. They were both 525's and had a hell of a time getting started in the spring. For some reason it seemed like the oil pooled in the injectors and made it very hard to get it out and get fuel through. I never expected to see that but both sets of engines were done the same and both had issues. It may be because the MMO didn't mix as well with the fuel as 2 stroke does.

30 seconds to remove the IAT sensor. 5 seconds to clean it with brake cleaner. 30 seconds to put it back in. 0ne minute and 5 seconds of annual maint service. No issue what so ever.

As for fogging an efi engine, salt is not the issue, condensation from temp and humidity fluctuations is.

PS, another easy way to fog efi motors is to pull a vacum line like the one going to the fuel pressure regulator. Connect a hose with a restrictor ( I use a vacum line reducer fitting worth 20 cents) and drop it into a bottle of 2 stroke oil while running the motor to heat it up. The motor will draw the oil in in small, metered amounts while running and coat the valves.

Fixx
 

Map sensor,,if that were the case then merc would not have the pcv going to any part of the intake including the hose from the valve cover to the flame arrestor. the engine is sucking not forcing the fogging oil into the sensors..

Well I'll be! Same thing happened to my 496..... never used MMO on it before last fall & this past spring it did not want to wake up.... won;t do that again!

we always pull the fuel filter, put a couple ounces of two stroke oil in the filter, and let it run, never had problems having hard starts in the spring, always fires right up. BTW this is on a 5.0efi

Mercruiser bulletin
 

Everdently you never read Mercruiser's bulletin. They present the proper way to fog a fuel injected engine.
mid it wasn't recommended why would they issue a bulletin on how to properly perform it

i learned multi port engines will hydro lock will oil easily if fogged

No. 2001-15 WARRANTY INFORMATIONSERVICE INFORMATION New Gasoline EFI/MPI Engine Fogging Procedure Models
All MerCruiser gasoline EFI and MPI engines produced in Stillwater.
NOTE: This change does not apply to carbureted engines produced in Stillwater or Hi-Performance engines produced by Mercury Racing.
Change Follow this new fogging procedure when laying an engine up for storage.
Fogging Mixture In a 6 US gal (23 L) remote outboard fuel tank,
mix: 5 US gal (19 L) regular unleaded 87 octane (90 RON) gasoline.
64 fl oz. (1.89 L) Mercury or Quicksilver Premium Plus 2-Cycle TC-W3 Outboard oil.
5 fl oz. (150 mL) Mercury or Quicksilver Fuel System Treatment and Stabilizer, OR 1 fl oz. (30 mL) Mercury or Quicksilver Fuel System Treatment and Stabilizer Concentrate.
SEPTEMBER 2001 2001-15 New Fogging Procedure
1.Disconnect and plug boat's fuel line from Water Separating Fuel Filter inlet.
2.Connect remote outboard fuel tank (with the fogging mixture) to the inlet of the Water Separating Fuel Filter. IMPORTANT: If the boat is out of the water, follow instructions for running engine on flush device as found in service manual for the engine being fogged.
3.a.Cool Fuel models: Start and run engine at 1300 rpm for 5 minutes.
b.VST models: Start and run engine at 1300 rpm for 10 minutes.
4.After specified running time is complete, slowly return throttle to idle rpm and shut engine off. IMPORTANT: Do not run engine's fuel system dry of this fogging mixture in the 6 US gal (23 L) remote outboard fuel tank.

^^^^ that's what we follow but with mid grade recreation - ethanol free or high test which is ethanol free up here

How much oil is being injected?

As for the talk about the ait and map sensor getting coated on fuel injected engines, if you put the oil in the fuel system and it goes through the fuel injectors, the oil never hits those sensors and also lubes the injectors for storage.