Fog when Changing Plugs?

[TOGA]

There's debate on whether or not you should fog the cylinders when changing plugs?

Some feel that fogging can foul the new plugs from the get-go.

Others see advantage in going ahead and taking advantage of having the plugs out to go ahead and fog and don't have a problem fouling the plugs at initial install.

What are y'alls thoughts?

I'm about to change mine and see if that brings my RPM's back to where they are supposed to be. I'd like to take advantage of fogging now while I have them out, but don't want to foul new plugs as soon I install them.

 

[biglar155]

Fogging is done in the Fall of the year before you put the boat away. You don't spray it through the plug holes (though you can for "extra" protection), you spray it into the air intake with the engine running.

The fouling issue comes from restarting in the spring. Best to start it up once and let it run for a while (on the hose of course) to burn the fogging oil out, then change the plugs.

YMMV

 

[Joe Hellaby]

There's no need to ever fog an engine if it's use regularly. The only need to fog an engine is when it's going to be sitting for an extended period of time.

When the engine gets used, it's designed to lubricate itself, that's what the oil is for. When the engine sits for an extended period, the fogging oil leaves a long lasting lubricant to keep rings, etc from drying out

There's additives you can add to your fuel to attempt to get your RPMs back (fuel system cleaners, and stabilizers with additives, etc)

Just my opinion

 

[GoVols01]

It's actually best to fog through the spark plug holes and not the intake. Reason being is the fogging oil coats the intake and any O2 sensors, which can slow the air movement through the intake manifold as well as foul your O2 sensors so they start throwing error codes.

I fogged my 12.5 KW Westerbeke generator every fall. I removed all 4 spark plugs, sprayed into each hole while I cranked the engine a few times over, then replaced the plugs.

Different strokes for different folks, but I prefer to not gunk up my intake manifolds.

 

[Julian]

I've NEVER heard anyone suggest you fog your engine when you change the plugs (UNLESS this is part of winterization). There has been debate about whether you should fog first, then let it sit over the winter, then start her up on the old plugs and THEN change the plugs. This makes sense to me if you are worried about the fogging oil fouling new plugs.

 

[Noko]

Ah, The fogging debate. What did people do before there was fogging spay? I try to fog the boat when its convenient. My boat sits from Sep to May, I have two snowmobiles that sit from March until Dec. I personally don't think it makes much of a difference either way. It can't hurt to fog but I really don't think that much rust is going to build up in the engine even if it sits. I've had snowmobiles for almost 30yrs and they always started up after sitting 9 months. I've had lawn mowers that have run great for a long time with no fogging. But when I do fog the boat, I do the intake and the spark plug holes. I don't spay a ton in the intake though. I've seen a video of someone spaying through the intake until the motor died. I've felt that was a little too much fogging. But I don't fog when just changing the plugs.

 

[KXCam22]

My plugs never foul. They have been in 5 seasons and fogged 6 times. Cam

 

[jdjetboater]

New to boating. What is fogging and what is considered an extended time of sitting idle? We get our boat out 5-6 times a year, not more than 3-4 weeks apart.

 

[biffdotorg]

New to boating. What is fogging and what is considered an extended time of sitting idle? We get our boat out 5-6 times a year, not more than 3-4 weeks apart.

fogging oil is used to winterize engines, or for any time they may sit for an extended period of time. It ads a layer of oil to cylinders and air plenums leading to the cylinder.

The OP years back was confused as the original argument was "should I change my plugs when doing the fogging in the fall as I have them out" and most would have said to run a tank of fuel though the engine in the spring before putting in the new plugs.

This is all practices that were done on two strokes on a regular basis. And it was easy to do with 2-3 cylinder two strokes as you sprayed it into the intake of a running engine until it stalled. Or into the plug hole. This practice was not common with 4 cylinder engines, as you couldn't stall a 4 cylinder engine by spraying into the intake. And the benefit was not noticed as much.

So like buttholes, everyone will have an opinion on this, but its' just not common practice on 4 strokes. To this day, the BRB Etec engines have an engine fogging featuer built into their sleds and Evinrude outboard motors. It's a cool feature.

Good luck,

 

[Matt Phillips]

I've fogged in the fall both ways...through the intake some years, and into the plug holes others. I didn't have enough daylight to change the plugs last fall so I did it through the intake...get enough oil in there and they will stall out. My preference is to do it while changing out the plugs as I know that gets a good layer of oil into each cylinder. It's never seemed to hurt the engines when they start up in the spring.

I'm also a proponent of changing out the plugs annually. I know that may be overkill, but in almost a decade of running both the MR1s and the 1.8s, I haven't had any days on the water with spark plug issues. I figure for the cost of a set of plugs and with the limited days I get to use the boat, that's pretty cheap insurance to not have to sit over hot engines on a 100 degree day changing out a set of plugs...with a 6-pack of people staring at me with that "can we go play now look?"

 

[Gym]

Here is a post from Mel @txav8r. from 2015. Its a bulletin from Yamaha that should put the debate to rest.

https://jetboaters.net/threads/mid-summer-maintenence.6235/post-106927

 

[NorfolkJames]

Check and adjust gap, Anti-seize on threads, thread in by hand, tighten with wrench. DO NOT OVERTIGHTEN.

 

[swatski]

Check and adjust gap, Anti-seize on threads, thread in by hand, tighten with wrench. DO NOT OVERTIGHTEN.

No gapping of NGK (6668) LFR6A spark plugs (for 1.8 n/a engines) is recommended.

No anti-seize is recommended for those modern plugs albeit that's debatable (I don't use anti-seize, but I replace plugs more than once a year). W/anti-seize torque values are off so best to do hand tight plus 1/4 turn.

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[biffdotorg]

No gapping of NGK (6668) LFR6A spark plugs (for 1.8 n/a engines) is recommended.
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Pre gapped plugs is like saying those new tires will not need to be balanced. (slight exaggeration) Sure they are brand new, and sure they are supposed to be to spec. But there is always that odd chance one went through the line and got bumped on the end and F'd up the gap. A gap tool is less than $1 and takes a second to check the gap before threading it in.

7 out of 8 were just fine when I put mine in this summer. And the one that was out of spec was really close. But still worth checking and adjusting.