I am having issues of running very rich and fouling plugs boat runs ok on the trailer I can very faintly here a slight miss when holding Rpms around 3k once it?s in the water it wants to hesitate and miss bad once u really get into it , has a 396bbc .06 over mild build
With a stage 4 cam engine pro performance camshaft ,Holley 670 carb 72/78 Jets mechanical secondary?s in the picture that was a brand new plug ran for about 5 min no black smoke ,Hei distributor brand new rotor ,cap , new module all spark plugs look exactly the same ,mixture screw are half turn out timing at 15 degrees at idle 35 all in compression about 150 psi all cylinders

Are the float levels in the carb adjusted right?


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The fuel level should be at the middle of the sight glass on the carb. If it?s at the very top of the sight glass it?s set too high and that?s more then likely your issue.


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Ahhh didn't read the post fully, I had a backfire on mine last year that messed up the floats level nd burned half my plugs.

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Okay I?ll do the bowl level , what would happen if it?s to full? It?s not coming out of the overflow tubes at all , and on the idle mixture screws one side seems to not do anything all the way in or back it out a few turns idle doesnt change at all,  1 screw each side for idle/air adjustment

if it is too full it will flow out of the boosters long before it will flow out of the vents as they are much lower.  typically the secondaries will spill before the primaries.  with the air filter off you will be able to see them leaking/spilling.  even on the trailer you could probably see it if someone wiggles the boat/trailer.

that is a problem with the idle screws.  the two that arent working should be inspected. 


New carb? old carb?

Mechanical or electric fuel pump?  What is the fuel pressure?

Oh ok I will check and see if it?s doing that not 100% sure on how a carb works , Mechanical fuel pump about 6.5psi on fuel pressure gauge that we just installed , old carb from the part numbers I looked up it?s looks to be a really old Holley not sure on the condition of it but it does look a little dirty by the air bleeds maybe rebuild time ?

Do you have the part # handy for the carb?  You said its really old but i didnt think older carbs have sight glasses in the bowls, just inspection screws.....

did you just put this carb on the boat or is this a "new to you" boat?

6r8026b is the only number I can see maybe p38 also and 7a choke horn is cut off

Fresh carb and fixed some wiring runs great now

great to hear.  didnt feel like chasing an old carb? haha