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I pulled out one side of plugs and don't know if I should just replace them or clean them up. I haven't had any fire problems it just I don't know how old they our. They might be OEM's from 03'. Here is a pic of what they look like. If I should clean them up, any suggestion on what to use. On my seadoo I used sand paper and WD 40. If you think I should replace them then what kind. 350 MAG MPI 300HP .

Also should I put dyelectric grease on the plug wires.
 

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Stokers Rule
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The pic resolution is not perfectly clear but it looks like those are platinum tip plugs. If so there is no reason to replace them unless there is noticeable errosion on the tips or a firing problem. The replacement schedule on platinum is three times longer than standard plugs.

Also be very careful about the method used to "clean" the tips. The platinum material is very thin and can be damaged or removed using sand paper. Very minimal cleaning is needed because the platinums will fire very well through some soot and debris.
Gently clean with carb cleaner and a shop towel should be adequate, and happy motoring :bigsmile:
 

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P.S. If you are replacing plugs my recommendation as a master tech is use the same thing the manufacturer put in it. The reason is: the resistance values through plugs are different based on make and the ignition system is designed for the specific values of the original plugs. Changing the plug values can lead to run issues which can be negligeable or huge depending on the application and ignition control system.
 

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This might sound a little strange, but remove the flame arrestor and at a high idle (maybe disconnect the throttle cable) mist a good amount of water down the carb (work the throttle to keep it running). Instant steam clean!
 

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You didn't say how many hours are on them, but those plugs are supposed to be good for 300 hours. They do look pretty dark.

They superceded those (AC 41-932) with AC 41-993. Don't buy the replacement plugs from a Merc dealer, they list for $18.00 per plug, they are available at discount auto parts stores for around $6.00.

Also, I would change the IAC muffler, a restricted muffler can cause a rich and unstable idle and blacken the plugs.
 

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I think he is referring to the IAC valve or Idle air control valve. Its located in the TB usually held on my 2 torx screws. It limits the air coming in to the TB during idle operations. There like a small piston with a point on it and retracts and expands as more or less air is needed to enter the motor to sustain a stable idle.
 

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TomZ said:
This might sound a little strange, but remove the flame arrestor and at a high idle (maybe disconnect the throttle cable) mist a good amount of water down the carb (work the throttle to keep it running). Instant steam clean!


An effective method but very harsh on an engine because steam can damage engine parts and if to much water gets spilled then a rod gets bent :shocked:

A more gentle method is to use transmission fluid. It also had a very high concentration of detergents in it which cleans well while some lubrication is still preserved in the engine during cleaning.


As mkos stated: a little time at wot will clean them right up :bigsmile: :bigsmile: :bigsmile:

Stick them in and run it :bigsmile:

Happy boating
 

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s022mag said:
You'll have to enlighten me on the IAC muffler, I have no clue what you talking about. And the motor has way less than 300 hrs.
If you remove the flame arrestor, there is a small block of foam in the inlet of the IAC air passage. This quiets the hissing noise made by the air rushing into the passage. It can become dirty and restricted, as I said before, will cause a rich idle mixture. The part # is 35-863892.



 

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Discussion Starter · #14 ·
Newport Dave said:
If you remove the flame arrestor, there is a small block of foam in the inlet of the IAC air passage. This quiets the hissing noise made by the air rushing into the passage. It can become dirty and restricted, as I said before, will cause a rich idle mixture. The part # is 35-863892.



I pulled the flame arrestor and that foam isn't there. :confused:
 

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They do go missing sometimes. One possibility is it got blown out of place by a backfire and then ingested. I have also heard they can get sucked into the IAC valve, but I have never actually seen that happen. You may want to check the hose that goes from the throttle body to the IAC and the valve itself.

But they do work pretty well at quieting IAC intake noise, you should notice a difference when you replace it.
 
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