Originally Posted by steveplumber
and fuel fittings which were only rated for smaller engines! would going too large on the fuel lines cause a loss of pressure?
Too large won't but too small will.....
I carried my my portable tankage from my old Suz 25 to a Yam55. Used the 1/4" hose / barbs / small primer etc, which ran fine with the Suz. I couldn't keep the Yam at WOT for more than about a minute before it konked out.
One upsizing to 3/8" later and it ran fine.
going from 8 to 10mm gives approx 50% more cross section for te fuel to flow through.
At a high level, think of it that a bigger engine will drink more fuel per second. A bigger diameter pipe means the fuel doesn't need to travel so fast through it to get a given volume through per second. Same goes for fittings. It's an unfortuinate law of physics that essentially says "as speed goes up, so does drag". As the drag increases, your fuel pump spends more of it's effort overcoming the drag than moving fuel, and you see the result as fuel starvation.