advice for cleaning 2001 40hp mercury powerhead before and after machining

james-ky

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Oct 24, 2017
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I am in the process of rebuilding my 2001 40hp mercury powerhead. I have the powerhead completely disassembled such that all that remains are the thermostat housing (and internals), brass plug at the top of each cylinder and a check valve (with hose) connected between the two cylinders. I am looking for advice on a few things. Before I take the head for machining should the remaining items I mention be removed from the powerhead? Also, what type of cleaning process is best practice both BEFORE and AFTER the powerhead is machined?

I appreciate any guidance.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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your machine shop will run it in their Hotsy prior to doing any work

when you get it back, a good bath with dawn dish soap and hot water, then use the leaf blower to dry it. wet a clean lint free cloth with oil and oil everything
 

james-ky

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Oct 24, 2017
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Ok, thanks for the response. Should I remove the components I mentioned in the post (thermostat, etc.) prior to machine work? Also, there is an extreme amount of carbon build up, would it hurt to have the powerhead hot soaked again after the work is done?
 

tommarvin

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Nov 22, 2015
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I would remove everything, but im not sure, the shop will clean the block before they bore.
If you feel like cleaning the carbon off go for it.
When you get it back from the machine shop I would do what Scott Danforth said to do above, Then watch you tube to put her back together.
You should get a factory service manual if your not sure.
 

Scott Danforth

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talk to your machine shop. each machine shop is different
 

rzrbkrd

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Aug 18, 2017
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If machine shop doesn't meticulously clean the block after machining then take it to your local car wash(must have hot water) and use the tire wash feature first as it cuts thru any oil film still in the block and then use the hot soapy wash to finish it. That should have enough pressure to get rid of any chips left in the block after machining. Take it home, blow it dry and oil cylinders immediately. My 2cents
 
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