back draft carb

[jsimms724]

I did a search on here and I know this has been discussed at great length (to bb or not bb)I have 1984 inline six 115hp . Since I have had this motor about a dozen guys have told me I need to plug the tubes (see photo) . When I ask why I get a dozen different answers . There is nothing wrong with my motor . It runs great, pushes my my 17ft fiber glass fish n ski 44mph,wot 5300 good hole shot. pulls the grand kids tubes effortlessly . One guy said the back draft carbs waste gas.that would be the only reason to consider the bb I know that the inline six motors are thirsty creatures and we spend a lot of money on gas. I am hoping that a merc guy on here can tell me if it will save me money As always thanks in advance.

 

[Chris1956]

Re: back draft carb

Actually Backdraft carbs are designed to save fuel by leaning out the mixture at mid-range RPMs. Sounds like that guy is confused.

Specifically, as the motor revs up, it pulls more air thru the tube into the carb throat. Eventually the backdraft jet cannot allow that volume of air to pass thru. This creates a vacuum in the float bowl chamber, which restricts the amount of fuel that is drawn thru the main jet, leaning the mixture. Some guys fear that the mixture will get too lean, leading to high temps and other bad things.

I have never had any issue with the Backdrag carbs.

 

[Georgesalmon]

Re: back draft carb

+1, I had the same issues, to BB or not to BB. I think it may have even been Chris1956 I listened to when rebuilding my carbs on a 1979 1/2 (no distb) 115hp inline 6. I decided to just replace the old backdraft hoses and leave it alone. So far, the motor runs fine at all speeds. Do I know if there are any fuel savings or fuel usage differences? Nope, but it runs great and thats important to me.