marine carb clarification
 

Been looking for a carb. I was always under the impression a holly marine carb had the J tube. I can't tell you how many I've looked at and was told that's not true. What's the story??

Holley marine carbs do have J tubes. Its a USCG safety requirement.

Marine Holley's
 

Throtlle plate shafts o-ringed so gas doesn't leak out

are you sure on that...I have pulled the shafts out of some marine holleys and there were no o-rings ? Rob

I don't know about o-rings, but all the Holley's I've pulled apart have had white teflon bushings in them. This is to keep them from sucking air. Thus helping to keep air to fuel ratios correct.

I have a marine Holly 800 dp just rebuilt for sale.

Not sure about o ring thing, I haven't pulled throttle plates out of a marine holley in years. But I remember there is some thing different around throttle plate shafts so when it floods bad, gas doesn't leak from shafts out on to engine. It keeps the gas contained in carb and dumps into engine. I know I have a book or article somewhere about the difference, I will have to try and find it.

I bought my last Holly 850 carbs from A.E.D. and they know what they are doing and the only difference is the J tubes are turn around to face the intake of the carb.

So basically "no j tube", "no marine carb".

If J tube is only difference then change them and you would be all set???

Some of the older marine carbs from Mercury did not have j tubes.

From Mr Dennis Moore's Book... (a personal favorite of mine) As well as the J-Tubes:
"Throttle shafts are grooved and slabbed to prevent fuel from leaking out of the throttle shafts if the accelerator pump is activated without the engine running, or if the engine is flooded. The grooved and slabbed throttle shafts direct the raw fuel back into the intake manifold where it is consumed by the engine."
For what it's worth, I run a BG Demon (non marine) carb on my BBC. I do hope not to blow up someday!

1) fuel pump vapor nipple
2) J tubes
3) teflon bushings on throttle shafts

I know those 3 three things are USCG mandatory

Final Answer
 

Holley Marine Carb We all know about J Tubes The Throttle shafts are grooved and slabbed to prevent fuel from leaking out of throttle shafts. The groved and slabbed throttle shafts direct the raw fuel back into the intake manifold. If a flood condition should happen.
Calibration; richer pump shot and mian metering circuit activated at lower rpm.

This is from Dennis Moore's book. Big-Block Chevy Marine Performance from HP Books. Section 1 The difference between Automotive and Marine Engines. Section 1 covers Electrical Systems , Fuel Systems, Fuel Pumps, Carburetors, Hoses, Crankcase Breathing, The book is a most for perfomance boaters doing there own worK