Help ......Trouble with Holly carb

[Donzigo]

Ok, I have two newly rebuilt Holly 650's on two 454's in the Z-33. Engines are 1996 models. A strange thing happens and has happened for over a year. After asking the folks on the registry, most of who said rebuild, I did. But, it's still happening. The starboard Holly after running at high speeds 3,600 / 3,800 rpm's for 30 minutes or so, runs real rich. When I back off and idle the boat, the thing bilches this black smoke for a long time. Then, after running the boat at slower speeds or idling for 10 to 20 minutes, she's fine again. No black smoke......until high speed again.

I can't figure it out........anybody wnat to take a shot at the cause?

[BUIZILLA]

okay...i'll bite..

secondary float level is too high, or secondary needle and seat is slightly sticking.

J

[Rodger]

That's what I would have said if Buizilla didn't answer first.

[Donzigo]

Thanks to you both. I had lunch with a mechanic pal todaya nd he said: "Sounds like your secondary float is sticking".........just ask the people who know and you get the right answer.

Now,to fix it. What? Re-build again?

Can I take it apart and do anything without the carb tools or specific know-how?

[Fish boy]

Richard, are both doing it and have both been doing it or did they start at different times?

Never done a holley 650, but my brother and I did my mom's 4bbl about two weeks ago. Had stuck float. It was not a super complicated procedure, actually took it apart in the detail area of lighthouse point high and dry. Only special tool needed was a screw driver that is sort of like an alan wrench but the tip is in a star formation rather than a hex. Not sure what it is called, but ended up with one in my screw driver set and did not know what it was for.

[Fish boy]

Not sure if this is the exact model, but it may be of some help

http://www.holley.com/HiOctn/TechServ/TechInfo/f4150-60.html

[Rootsy]

If the float setting is just too high it is a fairly easy adjustment to make. On top of the float bowls is what appears to be a hex nut and a round slotted screw head.

you are going to want to adjust the floats with the boat in the water and the engine @ idle. Remove the sight plug (slotted round screw)on side of float bowl. you are going to want the fuel level such that fuel just barely trickles from(is even with the bottom of)the sight hole.

To adjust grab a 5/8 box end wrench and put it around the nut, next take a LARGE screwdriver and loosen the slotted screw head. To lower the float turn the hex nut clockwise and to raise the float turn counterclockwise... if the slotted retaining screw backs off too much you'll have gas leaking from the needle/seat assy so keep it a bit snug but loose enough to adjust the needle/seat up and down. when you are satisified with the float height tighten the slotted screw against the hex nut and then tighten the hex nut against the float bowl...

of the needle and seat is sticking or float is down you will need to remove float bowl to evaluate... 5/16 box end wrench for a secondary bowl only needed.. unless it is a dual feed and then you'll have to remove the fuel line to that bowl also... I am assuming a vacuum secondary carb here...

if you have brass floats make sure that the float is not LEAKING... and that the return spring is under the float arm which helps to hold it up. Also make sure that if there is a baffle installed it is not interferring with the float operation. Lastly check the needle and seat for free operation by removing and flipping it over and back.. should move freely within itself.. ALSO... marine carbs should have spring loaded needle/seat assemblies which are not all self contained... this keeps the needle on the seat under very bumpy conditions...

[MOP]

Fish Boy that tool is called a Torx tip. Its worth having a set they are cheap.

[Donzigo]

Many thanks to all who replied. I'm taking the carb off tonight and bringing it up to the house to work on it. MadPoodle, what's your fax number, I'll get the number and send it. Thanks, Fishboy, for the breakdown. Rootsy, thanks so much, great post, printed the explanation for my work instructions tonight. How can I .do the work and leave it in the water? Disassemble onboard?

Fishboy, only happens to the port side engine, sorry, I think I said starboard, earlier.