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Should a MPI motor be fogged

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WarrenBoatguy

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"Looking for opinions on foggi

"Looking for opinions on fogging fuel injected I/Os. Should it be done? Is it pointless? The Mercruiser manual doesn't say it should be done, and outboard manufacturers say not to on their products. Any opinions?"
 
"Yes, it should be fogged. You

"Yes, it should be fogged. You need to protect the cylinder walls and valves, regardless of the fuel delivery system. Temperature inversions cause a lot of condensation and the moisture will make the cast iron and steel rust pretty quickly.

There will be other replies and more elaboration on this, I'm sure."
 
"The current debate regarding

"The current debate regarding fogging is not based on the type of fuel delivery system, rather the engine type.

The latest generation of GM engines (8.1 and 6.0) have 0.00" piston to cylinder wall clearance. Their hi-tech pistons are designed to expand and contract at the same rate as the engine block, thus, longer life, better performance, reduced oil contamination with less oil usage, etc.

It is for this reason that fogging is forbidden by most, if not all, of the marine engine manufacturers.

I know it is done, but that is the rationale behind their decision. The risks of internal damage caused by this mass of oil is greater than the risk of damage caused by not using it.

Rick"
 
"OK, but if the motor in quest

"OK, but if the motor in question isn't the same kind (cast iron vs aluminum), it should probably be fogged, right?"
 
"Absolutely! It is my opinion

"Absolutely! It is my opinion that any motor other than those specified above should be fogged, although I never agreed with pumping oil into the cylinders as many people do. More times than not, people get carried away and end up hydralocking the engine due to excess oil in the cylinders. All that excess oil only lays on the top of the piston anyway. A light coating of oil will protect the cylinders under even the most extreme conditions. This can be acheived by fogging through the intake with the engine running."
 
"I never liked hearing about p

"I never liked hearing about pumping oil into the cylinders, either, especially when they say that it should be turned over a couple of times and then put the plugs back in. Spring comes, they smoke the starter and wonder why. Not as if fogging is a new thing, anyway.

Re: the new motors and tight clearances- IIRC, they went back to matching the pistons to the motor and much tighter tolerances for this. I only went to one class on these and it was 6 years ago. Since I don't work on boats anymore, it's not something I remember completely but could look up."
 
"Good point, Jim. It's am

"Good point, Jim. It's amazing how our engines survived without fogging for all those years!

Jeff"
 
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