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Tight spark plug - what to do?

M

metal-chicken

Regular Contributor
I'm just going over our 225 and am pulling the plugs (new in April 2016) to check them and add some copper grease to the threads.

Everything fine apart from #5 (or is it 3 ....... bottom plug in the right hand bank) which is tight to undo while the others came out easily. I can undo it a bit but then it tightens up.

For now I've just sprayed some WD40 in and tilted the engine up a bit to keep the liquid down at the plug.

So what should I do now, leave it to soak overnight then put more effort in or something else?
 
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Thanks Chris - I was thinking that might be the answer!

The boat is currently in my barn but I'll see about setting up a tank of water and giving it a run this weekend.
 
Rats, couldn't wait until the weekend so I rigged up the tank and ran the engine for a good 10 mins and then tried the plug again - it was still tight but better and I got it out but...... cross threaded plug..... see my new thread :(
 
Its not cross threaded. It galled. The threads of the cylinder head stuck to the spark plug and were torn off the head. Thread repair is in your future. You should have tried to run the engine until it was hot. 10 min is to short.
 
Metal-chicken - sorry you've had that problem. When I first joined this forum, one of the participants (I can't recall who) strongly advised that every time you do a 100-hour oil change, pull the plugs and coat the threads with high-temp grease. I know it takes longer and that you need to loosen the right cowling to do it, but it's worth the trouble. Pulling those plugs also gives you the opportunity to check whether you are getting a clean burn in the cylinders and gives you an early warning if something is going wrong.

Just repeating here for others who come across this thread.
 
I recommend that you use the spark plug thread repair made by TIME-SERT. TIME-SERT spark plug repair kits are used extensively in the automotive repair field and are universally considered superior and more reliable than HeliCoil and other systems. Consequently, TIME-SERT is more expensive to use.

You can find TIME-SERT on-line and I believe they are now sold on Amazon. However, if you have any doubts about doing the installation yourself, you should find a competent shop to do it for you.

Good luck
 
Thanks for the info guys. Yes, I was working on the basis of pulling the plugs every year at least to check on their condition and apply anti sieze - unfortunately it seems this plug has been left untouched by someone just because it had become tight.
Money is not really a massive issue and we'll do what's required to put this engine right.... But it's rather not pull the head of we can avoid it!
I've read that timeserts seem to be better than helicoils in this instance so that's what I'll be going for.
 
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