Fogging a MPI 502

[scoflaw]

This engine will be laid up for at least 6 months. Although a no/no about using fogging oil thru the throttle body, has anyone done it ? Don't understand how some oil will ruin my sensors. I would feel better getting fogging oil through the valves. That cocktail mix of 2 stroke oil that merc recommends is a joke. If that actually works, why would 2 stroke owners fog their engines ? Fogging oil has a much better cling factor for sure.

​Just wondering if anyone has done it, by accident or otherwise and what were the results ?

 

[tpenfield]

Don't tell anyone, but I fogged my 7.4 MPI's with 2-cycle oil through the throttle body . . . Only done it once so far.

with the engines idling, I got about 6-8 ounces of 2-cycle oil in a bottle and took a 3/16" ID tube and put it up to the hole in the throttle plate . . . It sucked the oil down in about 10 seconds.


The fogging cocktail is a PITA to administer, but I have 'perfected' a method where I drain the fuel tank, then add about 5 gallons of 'cocktail' and run the engines on that mix while doing the winterizing/draining.

 

[QBhoy]

I have been strictly told by the Merc dealer not to fog the MPI. Causes more problems than it's worth.
Just a thought.

 

[QBhoy]

Only after I didn't it though...haha. I have had sensor problems since then !

 

[scoflaw]

I'm about ready to be the test dummy this fall, how bad could it get ? 2 cycle oil is like water compared to fogging oil. Usually I don't fog at all for a 5 month layup. Looking for maximum protection this time around. Someone must have tried it

 

[QBhoy]

Yeah...I have and have also run a slight mix of 2 stroke in the tank...had a few sensor problems later. Unsure if they were related.

 

[Scott Danforth]

your over thinking it.

run some 2-cycle oil in your tank - this actually stabilizes the fuel a bit in the injectors and coats the intake tract slightly. then pull your plugs, spray in some LPS2 in each cylinder, then rotate it 2-3 revolutions and spray some more in. put plugs back in and drain all water from manifolds/block. change oil and filter. since this is long-term storage, this is where the merc manual says to pour in anti-freeze for corrosion protection into the thermostat housing with a funnel.

if you really want to worry about storing a motor for long periods of time, pull the valve covers and remove all the rockers to un-compress the springs. then critters cant get in the combustion chambers and build nests and the valve springs wont be sitting for long periods of time with a valve open and spring compressed. make sure to tag the motor that the rockers need to be re-installed. that way when your 6 months becomes 6 years or 16 years your motor will be good to go with only pulling the dizzy and priming the oil system

once you understand what the 2-stroke oil is doing, the process listed in the merc manual is fine.

 

[scoflaw]

I'll plug my exhaust at the transom, not going to go through the effort of releasing rockers. I'm saying the 2 stroke oil isn't doing enough.

​I own an OX66 which is a fuel injected 2 stroke. If 2 stroke oil is good enough, why does Yamaha say to fog it, thru the throttle body. for long tem storage, with fogging oil. The OX has all the sensors the merc MPI has. No sensor issues with that motor.

 

[Bondo]

If 2 stroke oil is good enough, why does Yamaha say to fog it, thru the throttle body. for long tem storage, with fogging oil.

Ayuh,..... 'cause long term storage is measured in Years, 'n not months,....

 

[HT32BSX115]

Ayuh,..... 'cause long term storage is measured in Years, 'n not months,....

That's right. My last (1966) Mercruiser boat engine went idle nearly 9 months every year for 39 years before I sold it. It was never fogged. It lasted 39 years! It was getting a little worn out though......The hr meter quit in the mid 80's at 1500 hrs......I sold it in 2005. I am thinking fogging would have made no difference.

My Current 1997 7.4L Mercruiser engine is usually done in Aug and I don't touch it until June or July every year. I've had it since 2006. I never fog it.

I am thinking fogging probably isn't really necessary and neither is 2-stroke oil in the fuel. 2-stroke oil is for 2-strokes! This year my boat will sit from July until next June or July so I drained the 25 gallons of fuel that was still in the tank (leaving only about 2 or 3 gallons) I'm not putting any snake oil in the little bit of fuel remaining either. (I think the stuff is a little overrated.)

Regards,

Rick