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Stuck spark plug - BF150

T

TritonFisher

Contributing Member
I have one plug that will not budge and I’m hesitant to put too much torque on it as I would end up with a sheared plug. I added PB blaster, allowed for a two day soak (tighten/loosen) sequence to get the fluid down further and still nothing. My fear is that it is cross threaded as well.
1. Do I continue to be patient with the soaking?
2. If the motor is running fine, do I wait till fall and then go for it? If the plug breaks, I know the head has to come off.
3. I’ve read so many of you taking the heads off these Hondas-I have the online manual. Is it hard to do? I do the water pumps, VST, have rebuilt trim pumps, etc. my biggest fear is having the cams not lined up on reinstall.

Thanks!
 
Viberating the plug base will allow the PB Blaster to better soak down around the threads, After soaking with the PB Blaster, slip a ratchet over the ceramic part so it rests on the top of the metal base of the plug, then tap, tap, tap a bunch of times. Keep working at it that way. An alternative would be to use an impact driver - the mechanical kind that you tap with a hammer. Just don't overdo it.
 
You don't say if the 3 plugs you pulled out were oem NGK IR IZFRBK11 plugs if it is? its an iridium plug run it to failure which will be a long time. Its to deep down to tube to be messing with, just spray little kroil or blaster but not so much you ground out the coil. Run the motor. let it get hot and cold and keep spraying every once in a while then attempt with 6 point plug socket with a extension and use 3/8 socket wrench. If you use bigger 3/8 socket wrench you take a chance that you'll snap the hex off the spark plug leaving the threads in the plug hole. Also Is it stuck in the number #4 cylinder. I have seen four BF150 engines and two 225 all blow corrosion holes in the exhaust side of the head in the #4/5 cylinder. Only explanation I can think is there is an electrolysis issue with the engines combined with the heat and acids of the exhaust when they are racked or on lifts where the engines are kept straight up and down. This may also cause the #4 spark plugs to get stuck. As the one I snapped was the #4. Recommend tilting the engines up like on a boat trailer. keeps water from sitting in the thin head casting.
 
It is the #3 cylinder. Last long run had a little more steam than usual and I wanted to check the plugs which is how I found the issue (new in spring). I suspect it’s running hot (alarms work and no alarms on 75 miles on Monday). Plugs 1 and 2 look like the attached. IMG_6934.jpegAlso checked both t stats in water in the stove and the poppet. Dropped LU and did a vinegar flush which got some stuff out. I read to just run the hell out of it which is what I most likely will do as the plugs should last a while.
 
Are you sure that is an iridium-tipped plug? It doesn't look like it, but I really can't tell from the picture.

And assuming you do get the plug out, a lesson learned. Every time you do a 100-hour maintenance, pull the plugs and inspect the burn. Then re-install with a small amount of high-heat grease rubbed on the threads.
 
Agree with chawk_man. Doesn't look like an Iridium plug to me either. Iridium tips I've ever seen are pointed.

Have you tried breaking it free while the engine is hot?

Although, you're probably right, just run it. As long as there's a plug firing in the hole, you're on the water and that's what it's all about.

Good luck.
 
Based on the picture It looks like you have corrosion on the threads of that plug. I suspect the #3 stuck plug has the same thread corrosion issue hence why its stuck. Also doesn't look like iridium plug, so once you do need to get it out you could pull exhaust manifold which only takes a few minutes with a floor jack and 2x4 to pop it up, can reuse the gasket if you do it carefully. once that is off turn engine by hand 19 mm socket on pulley wheel bolt til exhaust valve opens and shoot blaster into the cylinder head and let it soak for a while. Beats snapping the plug and pulling the head.
 
Thanks for everyone’s help. Since I last checked this, I’ve run over 160 miles, and despite a few rough startups, it smooths out in a few seconds and has no change in performance.

It looks like this will be a fall project—HonDan I’m not sure about the manifold procedure. I assume that is with the LU removed?
 
On the old Ford Triton engines, that were infamous for spark plugs snapping off in the heads, one "technique" that had a good deal of success was to use an air impact to spin 'em out while hot.

Yes, it's risky but it's worked many times and if you're considering pulling the head anyway, might be worth it.

Just sayin'
 
Wanted to post a follow up on this. Ended up getting a poor idle and surging/bogging last time out. It alarmed (MIL) long on and off, but when I checked the code at home no dice (alarm went away, which is odd).

So I decided to take out that plug. PB blaster—no dice. I ended up going with an electric impact. Took it slow but it worked. Nerve racking is an understatement.

Got new plugs…This one won’t go in more than halfway. Not good. Got a thread chaser and chased all the way through, still only halfway. Got a reverse chaser. Those are too short for these plug tubes. Got a 4” 1/4” fine bolt and threaded it into the reverse chaser. Now I’m in business. An hour of back and forth, going slow and taking it easy. Tried the new plug again and it went in perfect. Removed, did a compression check (perfect) and reinstalled all plugs.

Now that I conquered the plugs, with a new high and low pressure filters, vst spotless, iac cleaned…..

Still stumbling after idling for ten seconds, then clearing itself, but this is what it did before the bad outings.

So—what’s next?
 
You might try pulling the vacuum control line from the fuel pressure regulator and checking to see if it's dry inside or wet with gas.

I see some of these had a solenoid valve that's associated to the IAC. If yours has one, do you know how that functions? I don't have any SI to reference....just mentioning it.

I guess at some point you may need to do some fuel pressure testing if nothing else jumps out for you.

Congratulations on getting that plug out and cutting threads. I know it took "guts~n~pucker"!
 
The O2 sensor also comes to mind. I'm sure I've read about them causing "runability" problems and not setting codes before.
Just another guess.
 
I had a spark plug stuck in my 225 about 7 years ago, finally got it out but the threads in the head were knackered.
Took the boat to my local motor garage and they fitted a Timesert (better than a helicoil for something that's repeatedly removed) for about £40GBP.
Job sorted, been fine ever since .

Make sure you remove the plugs every year to help stop the seizing into the head.
 
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