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Knock sensor stud removal


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I have had my ‘06 247 since 2008 and it’s always stored in my insulated shop in California (Central Valley). I always drain the manifolds and removed the impeller, but have never drained the block (remove knock sensor studs). I have never had issues, but thinking of starting to put RV antifreeze in to slow the corrosion/rust in the block and heads.

Anyone ever had issues removing the studs from the block that haven’t been removed since new?  I just am worried about them breaking off and making a bigger issue. 

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Ouch, 15 years. Those are steel and I would buy 2 replacements before you even start to pull them because they are going to be shot. I would liberally spray both with some form of penetrating oil and then let them soak for a good while. Then go sacrifice a goat or a virgin to the rust and corrosion gods because it is going to be a religious experience to get them out without stripping threads out of the block. A little heat on the block might not hurt either. Good luck. Bill

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I would think after 15 years, trying to slow corrosion with antifreeze is a lost cause.  That being said, you could just suck in a bunch of antifreeze w/o pulling the plugs and probably achieve your goal.

Edited by Rednucleus
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At some point the block/sensors will start to leak (in the middle of boating season of course) and potentially quit working if they erode enough. IIWM, I would address the issue now while I was messing with it.

  • Like 2
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I'm with @wdron this.  I think you should order replacements and have them on hand when you pull them.  It makes no sense not to and they're relatively inexpensive.  I pull them every year on my RLXi and they're getting replaced this spring as part of routine maintenance.  

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Ok i'm going to pull them. Just worried that they could break off inside the block since they have been in for years. Looked at them last night and no leaks or corrosion on the outside, so maybe they will come out easy. Should I just use pipe dope when installing the new ones which are now brass? Mine are the old style. 

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46 minutes ago, attilio said:

Ok i'm going to pull them. Just worried that they could break off inside the block since they have been in for years. Looked at them last night and no leaks or corrosion on the outside, so maybe they will come out easy. Should I just use pipe dope when installing the new ones which are now brass? Mine are the old style. 

use the standard antiseize paste

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For my 2008, I bought the updated Brass and Post kit for the knock sensor after the first year of winterizing it.  The brass stays in the block and the stud bolt comes out with the sensor.  Only downside is it takes longer to drain the water as the hole is smaller.  You can get the stud kit @ Bakes.  

image.thumb.png.088394e224d1643206239ae4b3152ee1.png

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  • 2 weeks later...

I pulled out the knock sensor studs and the look perfect. No rusty water came out and all threads look good in the block.

What is the reason that Indmar changed to the brass fitting with steel bolt?

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4 minutes ago, attilio said:

I pulled out the knock sensor studs and the look perfect. No rusty water came out and all threads look good in the block.

What is the reason that Indmar changed to the brass fitting with steel bolt?

Probably people pulling the studs and leaving them out so the block threads rust to death over the winter.

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