jhofmannjhofmann ConnecticutPosts: 372Member ✭✭✭
Over the years I have always sprayed fogging oil down the carb until the engine stalled as part of my winterizing process. I now have throttle body injection, and have been told not to fog it as it will effect the sensors. Is it necessary to fog the engine (Merc 5.7) 


  • StodgeStodge Lake St. ClairPosts: 1,925Member ✭✭✭✭
    As I understand it you don't fog injected engines.

    2002 FV 342 on Lake St. Clair - Past Commodore SHC - Vessel Examiner USCGAUX

  • Dream_InnDream_Inn Annapolis, MDPosts: 4,493Member, Moderator mod
    I've never fogged my injected engines over the last 10 years of owning them. 

    Dream 'Inn III -- 2008 400 Express

  • frenchshipfrenchship Québec ,CanadaPosts: 1,079Member ✭✭✭
    If you have mercruiser there is a recommendation how to mix some gas with two stroke engine oil and some stabilizer and running it thru the engines for winterizing.
    if you don't find the recipe let me know ang I will send it to you
  • frenchshipfrenchship Québec ,CanadaPosts: 1,079Member ✭✭✭
    We don't fog injected engines.
  • Liberty44140Liberty44140 Bay Village & Marblehead, OH.Posts: 1,753Member ✭✭✭✭
    I have twin 350 5.7 Merc MAg MPI and I mixed the cocktail this year. I mixed 2.5 gal of gas dock gas, 1 qt of two stroke outboard oil and an ounce of fuel medic stabilizer together in a 3 gal remote dinghy gas tank. I used next to no gas out of the tank winterizing both motors so I don't think the mix made it all the way through. Not even a quart was used. I don't think I'm going to do this next year as most on this forum with the same or similar engines let them sit for 6 months like I do and they don't fog. I am FWC so I only ran the engines for a few minutes each on the remote tank to get 3 gal of antifreeze per engine through the heat exchanger and manifolds after I drained the raw water out of the engines. I did not run for 10 min per engine as i do not have hose access inside and again I'm FWC so I dont need my thermostats to open to winterize like RWC does. 
    Wine-N-Down -- 2006 342 Express Cruiser

  • rasburyrasbury Sanford, FLPosts: 4,235Member ✭✭✭✭
    I think the fwc is for sure a plus, even here in fl. We had two weeks, prob 2 years ago it hovered around freezing the entire time- rare but it happens an for sure was 20's at night. I had no issues.
  • tniggeltniggel Posts: 57Member ✭✭
    Here are the official merc instructions for fogging an efi/mpi.  I never have done this, but for those who want to know what you're "supposed to do."
  • AlswaggAlswagg Posts: 2,215Member ✭✭✭✭✭
    Yes that is very common.  We simply use. 3 gallon portable tank.  I feel it is much easier to use.   This is how we service all of our boats prior to lay up.  Including old carbureted engines.   Old style spray fog oil damages air chamber sensors and can easily clog idle control valves.  I have also seen many clogged idle jets clogged by over fogging a carb 
  • jhofmannjhofmann ConnecticutPosts: 372Member ✭✭✭
    Thanks for the information. I almost tried spraying fogging oil down the throttle body. Old habits are hard to break.
  • pault1216pault1216 Indianapolis, INPosts: 188Member ✭✭✭
    I have always mixed the cocktail of 2 stroke oil with gas and stabilizer and pour it into a drained fuel filter. When it starts smoking I shut it down. This is after the end of season oil change. In the spring I replace the filter after about 10 hours so it has time to separate any moisture in the fuel from storage. No additional tank or hose switching required. It has not let me down yet (MPI and carb motors). Just my 3 cents worth (adjusted for inflation).  -Paul
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