Topic: How do the fuel lines get routed on my 1955 Mark 25?

This topic has 9 replies, 5 voices, and was last updated 7 years ago by dave-bernard.

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April 5, 2017 at 1:38 am #6683
huntleybill
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US Member - 2 Years
Because I was given this motor in pieces, I am having a hard time figuring out where the fuel lines go. Does anyone have a picture that shows clearly how they fit and which one goes where? There doesn’t seem to be a lot of room in that area. Would an illustrated parts breakdown show what I need?

Any help is always appreciated.
Thank you
Bill
April 5, 2017 at 1:52 am #55592
opposedtwin
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US Member - 2 Years
Here is a pic with the cowls removed. This is a 1956 but it’s the same for a 1955.

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April 5, 2017 at 3:40 am #55600
huntleybill
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US Member - 2 Years
Thank you for the pictures but Mine is different. It has what I think is a fuel pump that mounts to the side cover. Also, mine has 4 fuel lines. And, that piece shown in the picture that the 2 lines go into is not on my motor. There is a place for the two lines on mine but they screw into the power head.

I hope that makes sense.
April 5, 2017 at 3:56 am #55601
dave-bernard
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US Member
do you have a mark 25E or a mark20 pressure . got pics
April 5, 2017 at 3:46 pm #55621
austin78m
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US Member - 2 Years
Sounds like you have a Mark 25E. The starter bracket mounts where the fuel pump would mount on a standard motor. As a result there are additional hoses needed to pulse the fuel pump. The fuel pump is fastened to the starboard cowling by two screws. I just took mine apart. Let me see if I can get pictures tonight.
April 5, 2017 at 7:58 pm #55632
huntleybill
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US Member - 2 Years
Yes, it is a Mark 25E…I guess the "E" was important. Here are some pictures. Hopefully this will help. I do NOT know if I have the correct fuel line in the correct spot so please take that into consideration.

Thank you

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April 6, 2017 at 3:59 am #55657
dave-bernard
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looks good to me. in side from the fuel tank connector and out side to carb.
April 6, 2017 at 11:20 am #55664
Pete
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US Member
That fuel line from the fuel pump to the carb top looks a bit too sharp at the 90 degree turn. It already has the start of some restriction that could get worse with time. IMO needs a smoother curve. Is that a factory match remade fuel line, seems the crimp fittings are too long:?: Is that the correct carb for this engine with the elevated filter unit ❓

Look at this video (1956 mark 25E I know one year later but an example) starting at 2:59, shows a different carb top from yours with the fuel line from the pump going down to the carb top (maybe Merc changed carb and fuel line arrangement in 1956 ❓ ), are these shown OEM matched fuel lines ❓ :

https://www.youtube.com/watch?v=tCJgFEQUYlA
April 6, 2017 at 1:09 pm #55670
austin78m
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US Member - 2 Years
I just recently took my 1955 Mark 25E apart. There are two lines that need to be routed correctly so the crankcase pressure can properly pulse the fuel pump. Please see the photos below for the proper routing of those lines. The other two lines are for the fuel it self. The fuel pump is marked "IN" where the line from the fuel connector runs. The other unmarked hole is hooked to the carburetor. Hopefully this helps. If you need additional pictures please let me know. Best of luck to you!
April 6, 2017 at 2:55 pm #55673
dave-bernard
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US Member
that is the correct large filter for the mark 25 E. I had and worked on them.
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