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Merc 900 gas line internal measurement

haventaclue

haventaclue

Outstanding Contributor
1978 Merc 900 tower of power. New to me.
Fuel lines from pump to carbs are 6mm or 1/4".
I think too small as I have 9/16" /8mm on my Merc 800. Info on correct size appreciated.
All secured with zip ties.
I have scoured the search on the forum. So I'm guessing I'm not asking the right question:)
 
So what is your motor doing / not doing ?----What trouble shooting has been done?----What leads you to believe that fuel line is now too small after 43 years ??
 
I just purchased this motor and getting it fitted to the boat.
I know that the fuel line from tank, in the bow, has 3/8". I did this because of the distance. Normally 5/16". But previous owner has replaced all of the fuel lines on the engine it self with 6mm bore.
Due to a small incident in the past when I used a smaller bore fitting,6mm, on my '69 Merc800/80, it would choke when I would go wide open, I'm questioning my self whether the 6mm is correct.
 
The manual says 5/16" to 3/8" for the tank to engine line, [how are these internal lines connected], the fitting should give you the inside diameter probably 5/16".
 
The brain isn't firing on all cyls,mine that is. I.D of the fitting coming off the fuel pump to carbs is 5.5mm,so I would assume that a 6mm I.D. fuel line will be sufficient.:eek:
 
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