Whats this tube attached to the head of my Mercury 140 blueband

woodsyfeller

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Aug 15, 2011
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I was given "free" boat and engine a few years back and I am in the process of putting everything together now that I have the "title" issues worked out.Im pretty new to marine 2 stroke mechanics.Anyways on to my ?? there is a fitting placed on the head between the 3rd and 4th cylinder with a small piece of rubber tubing attached.I was wondering if that was for something special ,like vacum/water/oil guages of some sort. I was thinking it may be some sort of crankcase breather but that doesnt seem to make sense on a 2 stroke since the fuel/oil passes through the crank on the way to the piston.The engine is supposed to be 1980 140hp inline 6. I'm adding a pic to help show what I'm refering to.


PIC_3365.jpgPIC_3367.JPG


Thanks ahead of time for any info.
 

cr2k

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Mar 19, 2009
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Re: Whats this tube attached to the head of my Mercury 140 blueband

Probably a fitting for a water pressure gauge. Is it blocked off or open?
 

woodsyfeller

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Re: Whats this tube attached to the head of my Mercury 140 blueband

It is opened. It looks like it was cut off.If it is for a water pressure guage does it need to be hooked up to run the engine?Obviously it would need to be capped or blocked off first.
 

Gomer50

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Re: Whats this tube attached to the head of my Mercury 140 blueband

Doesnt need to be hooked up.Just block it off.
 

Chris1956

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Re: Whats this tube attached to the head of my Mercury 140 blueband

You do have a separate fitting for the telltale? If not, hook it to the telltale, as you will want that piece of mind.
 

Chris1956

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Re: Whats this tube attached to the head of my Mercury 140 blueband

Sorry, fat fingers. That is peace of mind.
 

woodsyfeller

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Re: Whats this tube attached to the head of my Mercury 140 blueband

I'm not sure what you mean by telltale. Im guessing its running it outside the unit so you always see water spraying showing impeller is working, forgive me I'm a newb to lots of terminolgy.
 
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relocyo

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Apr 14, 2010
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446
Re: Whats this tube attached to the head of my Mercury 140 blueband

Yup, tell tale = motor pee :D I would also say it looks like a tell tale,either cap it or run it to the outside as you dont want a steady stream of water pouring into the engine case... Or you could get a T connector and also run a water pressure gauge off of it and still have the "pee" stream for visual confirmation of impellar operation... Good luck! Post back!
 

Gomer50

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Sep 5, 2009
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Re: Whats this tube attached to the head of my Mercury 140 blueband

There should be a fitting just like that on the top of the block and a hose attached to it running down the side of the motor to the tell tale outlet on the right side of the bottom cowling where the fuel pump sits.Using the one on the back for the tell tale would in my opinion not circulate the water completly to the top 3 cylinders.
 

mr 88

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Nov 3, 2010
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Re: Whats this tube attached to the head of my Mercury 140 blueband

Better yet why not buy a gauge and hook it back up up? Cheap insurance for piece of mind that your motor is properly being cooled.Some of the stacks are known for smoking the top cylinders due to airlock up top or poor water pickup,weeds bags etc covering the water pickup.
 

woodsyfeller

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Re: Whats this tube attached to the head of my Mercury 140 blueband

There is a water pressure gauge on the boat so I think I'll be hooking it up, I was asking more questions to see what my options were.I'm learning as I go.I'll be asking tons of ?? as I continue to put this boat back together.Well thats one piece of the puzzle figured out now for the next 500 pieces.I guess my next question should be is what kind of tubing I should use is there a special tubing I should be aware of or would fuel line tubing be sufficient?
 

Chris1956

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Mar 25, 2004
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27,036
Re: Whats this tube attached to the head of my Mercury 140 blueband

Tubing for the water pressure gauge is any kind of cheep stuff you have laying around. The water pressure is never any more than 12-15LBS, if that much. Tubing for the telltale is usually decent neopreme. Cheap neopreme fuel line will work.
 
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