I have a problem....upon installing a OS 21 in my wildthing hull, I had to modify the mounts to fit the pull start which made the mount from 4" to 5" inches..my problem now is the 8oz fuel tank does not fit on the right side of the engine.....Does the OS 21 with a mac tuned pipe have enough back pressure topush the fuel through is I use two 4oz fuel tanks side my side to replace the 8 oz then the 2oz hopper tank infront of the engine
:unsure: Bear with me on this: What I have seen first hand on .21 boats with split 4 oz tanks was this.
Because of the flow restriction of the pickup and transfer tubing from one tank to the other when you run boat with full tanks then find the right needle you will run spot on untill the first tank empties then because of the lesser flow restriction of the transfering fuel the engine will run richer on the second tank and unless you have a third channel mix controll on engine to lean down slighty it will drive you nuts !!
A third tank ( Hopper ) will not help.
Reason for this is simple: As fuel leaves carbs spraybar, fuel upstream must be pushed/drawn to the main tank from the other tanks. In other words use 1 ounce from main tank it must be replace by another tank upstream with equal fuel used to equal fuel replaced. Every inch of tubing causes flow restriction and while pipe pressure on the furthest upstream tank adds to the transfering of fuel and some delivery pressure it is dampened by resistance and weight of the fuel it pushs along. At every point fuel no longer has to make the jump from one tank to another you gain greater flow even at the same pressure !! Big pick ups and transfer hose size will help a bunch but won't elminate this tendency. :blink: Scott
If u would be using a float chamber like we pretty much all do in Europe then u won't have this problem .We have to run 30 mins so without the float we would surely have this tendency .
